I have been paying attention to Linux for the last 2 years. Having been a Windows user since version 3.0, I really didn't think Linux was ready for the mainstream. I has a pleasant surprise with Ubuntu/Kubuntu and OpenSuse, the ones I tested. I cannot say I diskike it, but Linux still has a long way to go in user friendliness. On the stability front, I only recall having Linux crash on me once, so I have a pretty favorable idea of it. I managed to install everything I needed to watch DVD's, watch flash based content, and even a few games, the best one being Open Arena (uses Quake 3 engine). But there are somethings you must delve deep to do and I didn't have that much time to give to it.
Personally, I'm paying attention to Linux. It's great if you have a computer without OS that you will be using for Office tasks, but if you are used to Windows and like to game like me, it will, at best, be in a dual boot configuration, ora secondary PC. I won't switch to Linux anytime soon.
Having said that, I'm still using Windows XP SP3. I have a Laptop taht came with Vista Premium and I don't like it. It has caused me two major incompatibility headaches - even after SP1, which resulted in two full reinstalls (and I usually do a lot of research to try to cure the problem before I ahve to resort to that), and then from a usability point of view there are a lot of small things that make the user experience sub-optimal.
I have Windows 7 intalled on three machines, on in 64-bit flavour, the other two being 32-bit - one is on the laptop. I must say it corrects almost everyting I'm annoyed by in Vista, and it's a breeze installing drivers compared to XP - it does it all for you! I'm looking forward to the final version (and the RC on May 5th, of course)