I've use linux for many a years on and off, currently things are getting much much better than they used to be.
It tends to just work now
Been using Ubuntu few the past year or so and does everything I need, even run of a pendrive
I only run it on a laptop though at the moment,
Still have XP or Vista I forget which I'm using now on the desktop as I play games and other things that are simpler on windows as it's more powerful (the computer hardware that is).
I wouldn't say it was faster than XP, but about the same really (hey they can only go as fast as the hardware)
The cut down versions linux distro's (puppy etc.) can feel snappier though but still you can easily bog them down, lol.
If you surf the web, watch TV, listen to music (even streaming) or simple office things then it's perfectly fine.
I find the office programs lack still but if you do simple stuff they are fine, TV/Media is a rough affair and still not as nice as the windows counterparts.