In my experience, Windows 10 has been a good operating system. It's only real drawback is all the negative PR it's been getting, some of it deserved, some of it not. The OS feels and runs pretty much the same as Windows 7, beneath the 'new start menu', all the familiar things are in there. The Anniversary update make the new 'Settings' a bit more useful, but I still feel like the old control panel is still the best way to tweak things. I run a myriad of programs on my Windows box, including Visual Studio, cygwin and cygwin's X server, VMware, Steam and a plethora of games. All of these Windows 10 has run without any issues.
I refurbish old laptops at my place of employment. I find that Windows 10 is more responsive and runs generally faster on older hardware, such as 2GB RAM Intel Core2 laptops. Windows 7 really seems to crawl on such machines, where 10 seems to deal with the limited system better.
Hands down, the Update mechanism for Windows 10 is much much faster than Windows 7, but that's easily attributed to the fact 10 hasn't gotten several years of updates slapped onto it. It's not without flaw in this area, I've encountered some issues with the forced update in Windows 10. In particular one model of laptop I had many duplicates of has video hardware that the latest drivers for cause it to malfunction, requiring me to use a tool to prohibit an update from being installed, and that was a bit of a bear because the timing of getting the update removed, and firing up the tool to 'hide' it had to be just right or Windows would just reinstall the update. I found that annoying.
I can easily understand the justification for the 'forced update' mechanism, and while I might find it a little annoying, I think it's a good thing. We've for too long allowed clueless users to control this stuff and we as IT professionals have to deal with the fallout. Malware getting into machines that should have been patched, but the user postponed updates, or turned them off all together. This was the right direction to take, updates are mandatory, for everyones protection. Malware not only hurts machines it's on, in many cases, it hurts everyone when botnets are used to attack other services and servers, or send out unwanted spam mail. I think Microsoft did the right thing here.
As for the telemetry and 'strongly encouraged update to Windows 10 campaign', I think Microsoft really shot themselves in the foot with that. It's definitely a MUCH better OS than Windows 8/8.1, and I often have people tell me they heard 'Windows 10 is bad.' It's not really bad, Microsoft just made it look bad with their upgrade campaign. I think if Microsoft hadn't pushed that campaign so aggressively, this OS would be heralded much like Windows 7 was. Back to telemetry, this is a place where I think the tech industry's commentators have cast an unfairly bad limelight on Windows 10. Android does just as much telemetry if not more and no one seems to mind. It's just the progression of our technology that most applications and now operating systems like to collect data. People freak out their information is being stolen, but I think that's silly, the data is most likely anonymized and shoved into databases with billions of other data points from other computers. Ultimately I think it's not being use nefariously, rather it's being used to help engineers and developers understand better how their software is operating in a myriad of environments, and what people are commonly using it for.
As a developer, networking specialist, and computer refurbisher, I overall give Windows 10 a thumbs-up. It does what I need it to do, and doesn't get in my way. That's my experience.