It really depends on what gaming you want to do. Anything that doesn't require Direct X 10 or strange drivers that for some reason are Vista only (which is like 99.9% of all games/hardware) Just use XP.
Which is actually what I'm doing. But face it, XP is being phased out whether we like it or not. 3 years down the line the vista installation base has a lion's share of gaming rigs on plain windows tax inertia alone. At work, I recently upgraded W2k to XP for the sole reason of latest PCB design tools puking on W2k as it's not supported or tested against it anymore. Vista's creeping there too as well, unless you're big enough shop to have dedicated IT staff etc.
I went all Linux back in 2006, apart from gaming just about everything else works perfectly. I used Firefox to browse, OOo to write documents, and so there was no change in software. Today just about everything with Ubuntu can be done quicker than on Windows to set up a comparable system, it takes me less time to get a fully functioning Ubuntu box with DVD/MP3/a few programs/nVidia drivers compared to just installing Windows XP and getting all of the hardware to work.
Mm. No.
I wasted a week'n'half of my vacation last summer trying to set up a HTPC running on mythbuntu. Even after I scaled down the requirements to just getting something to "play" I was not getting anywhere fast. Linux audio is a big steaming turd and even really elementary stuff like getting SPDIF enabled is an adventure where you have to get comfy with mod parameters and the like.
Not to mention there are no system wide codecs all applications know how to use and so on and so forth.
That whole party line of "so easy anyone can do it" degenerates pretty fast into .conf hell if you want to do something "exotic" like use the digital output or multi-channel audio.
Ooo is just terrible compared to Office as well. I use excel a lot for various engineering things and just making simple solve-with-parameters table or a 2d chart to study component values is much more difficult than it needs to be.
Yeah, maybe 3.x release did something about that, but 2.x calc at least was really bad. I don't feel obliged to learn to use user-hostile software for ideological reasons, I just want to get my day-to-day work done.
To sum up my HTPC project, once I gave up on the whole geek-credibility linux idea, I had fully functional media-box running on top of XP within a few hours including reinstall from scratch. With ffdshow and media player classic everything just works and dvbviewer is remarkably straightforward to set up compared to mythtv or vdr.
My only mistake was wasting more than couple of nights on the linux-project. That's the engineering mindset that difficulties are made to be surpassed. But sometimes the tool is just wrong. I also tried plain ubuntu and debian to see if they make any difference but the whole "multimedia" thing doesn't seem to be there.