Obviously YMMV. I have had my share of weird problems with Macs, although none took more than 45 minutes to solve with the help of Google. Regarding hardware, there was a period around 2005 where their initial build quality left something to be desired, every system I bought in 2005 had to have a warrantee claim for some hardware issue. Systems before 2005 and after have been very high quality. En-toto, though, it's been much, much easier to keep them running ... and not one single full rebuild in the nine years since I started using OSX aside from a total hard drive failure.
I bought my first OSX laptop in 2001 to replace my wife's Windows laptop. I had been forced to rebuild that Windows laptop every 3 months like clockwork. (This was Win98, XP hadn't hit the scenes yet, although I'd been using NT for years on the desktop.) It drove me insane because rebuilds took 10 hours apiece between the OS reinstall and all the applications. (Reasonably priced imaging software was not yet available, nor back-up software for that matter.) We got the Mac (a Ti Powerbook) and I did almost nothing to it for its entire 5 year lifespan at home, and nothing at all for the 2 years after before the hinges broke from heavy use and destroyed the screen connection ribbon. 7 years out of that laptop and I spent less than *one hour* keeping it running. That is one heck of an improvement.
I thought XP would make things better, but it didn't. The registry was (and is) still a huge disaster, but luckily (or not) most XP boxes are so hugely malware infected within a year (sometimes within weeks) that you have to wipe and rebuild them. (Eradication is nigh impossible these days, and certainly much slower than a rebuild even when it works.) I don't own Acronis True Image because I felt like paying a bunch of money, I own it as a purely defensive measure: The Windows systems get imaged at every major installation point so at least I can return them to a near-current configuration within about half an hour.
Malware infections happen despite antivirus software. In fact, I find they're worse when using something mainstream like Norton versus something more oddball like AVG ... and most people use mainstream products.
Then there are the users. I had one who would randomly delete things. Like drivers. Her system would just stop working in weird and inscrutable ways, and of course she had no idea what she did. I finally gave up and forced her onto a Mac. I have had to deal with fewer than one issue per *year* since. That is another big improvement, and I think it comes down to the nice separation between system and user permissions; she cannot delete system things willy-nilly.
This is of course possible on Windows systems too (in fact, I gave a talk on how to configure your NT system's security back at WinDev in 1996) but unfortunately a wide variety of applications simply stop working if you are not running as administrator and people totally hate it if you lock the systems down so they can't install things. (That is true on Mac and Windows, although the Mac's security system is vastly less intrusive than UAC despite accomplishing the same thing.) The state of things on Windows has improved a lot since Vista, at least consumer games don't need admin rights just to run anymore, but I still run into it regularly with poorly written or legacy applications. It makes it quite difficult to convince users to run on securely configured systems.
I thought Vista would be a big improvement versus XP and pushed people to upgrade. I was mistaken. Everyone turns off UAC, the only significant improvement in the whole system, because it's just so intrusive. The first year to year and a half of Vista were disastrous due to immature and missing drivers too. But hey, most Windows users skipped Vista and went straight to Win7 so they missed that pain.
Win7 did not improve the malware situation over Vista, UAC or not. Both, according to the statistics, are vastly better than XP ... but it's very hard to tell based on the systems I get to disinfect. I think the quantity of successful malware infections is down, but when infected XP systems came in they'd be infested with four or five things while Vista and Win7 are usually just one or (rarely) two. Unfortunately those one or two are often the meanest and hardest to clean. So, back to wipe and reinstall. Fun fun fun! And when they're not systems I administer frequently I don't have an image and get to do the oh-so-lovely three hour Win7 install and update rigamarole, then a few more hours reinstalling all the apps. I *hate* that.
YMMV. My personal XP, Vista, and Win7 systems have not had any stability or infection problems to speak of, modulus bad drivers early in Vista. I spend little to no time managing them. I am clearly unusual, though, because I see plenty of damaged systems come through and spent stupid amounts of time fixing them. Macs, not so much. Every user who converted from Windows to Mac dropped off the radar in terms of administration overhead. The problem users no longer have systems that need major repair, but the depth of the repairs fell way off -- they now need really easy things like putting the URL bar back onto Safari, or making the Dock stay put.
Oh yea, no crapware to deal with on Macs either. And no need to buy and continually update antivirus and anti-malware (at least not yet).
Again YMMV, but I deal with Windows, Linux, and MacOS every day and of the three MacOS is the easiest to keep running, with Linux following a little behind. Windows takes a lot of time, with more problems and much more time-consuming solutions. And it did not get much better with Vista and Win7.
Regarding hardware quality, I agree that Acer does a much better job than Dell or Compaq. (For the last four years or so I have preferred Acer systems.) In the field they're not very common though, and in the end analysis the laptops not anywhere near as durable as either a Thinkpad or Macbook. All that plastic does not hold up that well. I realize it probably doesn't matter to you, I bet you replace such hardware no less often than every 3 years, and probably closer to every 2, just like I do with my Windows boxes. (Actually that's not quite true, the desktops get recycled into Linux servers and tend to pull another 3 to 4 years in that role ... I love Linux. But I have to repurchase hardware for Windows regularly because it continually gets bigger and slower to a degree where it is difficult or impossible to expand the system to keep up. Hopefully the hardware is getting sufficiently expandable now that the cycle will get broken.) But the Macs ... 5 years is a minimum and then they go off as hand-me-downs to someone else for years after. Newer versions of MacOS since 10.0 have worked better on the same hardware than the prior version. Leaner, meaner, more efficient despite greater capabilities. All told that is really good bang-for-the-buck in my book, particularly when combined with much lower administration costs.
 As an aside, Time Machine does a great job of this out-of-the-box. The one time I had a full hardware failure (a Mac mini's drive failed) the reinstall from backup was remarkably straightforward without any external tools. And it took less than half an hour. I really wish Microsoft would do a better job with in-the-box backup ... granted it's much better today than it was with XP, but it is still pretty lousy particularly on restore. Did I mention how much I liked Acronis?
 Some of the problems got much weirder, although not ultimately inscrutable. For instance, I had a user using a legacy app that would save a file and then try to load it in another app ... and it was not there. Go back to the first app, there it is. This was because of the virtualization of "Programs and Settings"; the app default was to save into a subdirectory of its install, and Vista virtualizes those directories to improve stability. Run a different app and it has a different virtualized directory so it can't see the file. What made it worse is that Search couldn't find the file in the virtualized directories -- they're specifically excluded (at least in Vista, have not checked Win7) -- and of course the whole directory structure is hidden from the desktop. The user had no chance of finding that file and was completely perpexed. It took me almost an hour to figure out what was going on too, until I saw the virtualization directory in the CMD shell and it twigged my memory about directory virtualization. I think the virtualization is too simplistic; it needs to share data files between apps per-user, but isolate DLLs and the like per-app. And no matter what form virtualization takes Search needs to be able to find stuff in those directories!
 The achilles heel of the Powerbooks was the power cord; when stressed it was not too difficult to break things inside the laptop. Unlike the Dells and Compaqs this was a daughterboard item on the Powerbooks and pretty easy and inexpensive to replace, so the laptop wasn't a loss if it happened. The move to the magnetic connectors has totally eliminated that particular problem. I rather wish Apple would license that to other manufacturers. What kills Mac laptops over the long haul today is monitor backlight failure. It's too early to know if the LED backlight systems common in Macs today will have similar issues to fluorescent backlights, although I suspect not.
 Win7 was the first new version of Windows in two decades that hadn't required double or more the resources of the previous (ok, ignoring WinME I suppose), and in the case of XPSP2 even the service pack doubled RAM requirements. Win7 didn't get any better than Vista in my experience, despite claims otherwise, but thank god it wasn't any worse. The Vista upgrade required wholesale machine upgrades, very expensive....