I'm using Win 7 on my mail laptop and XP on 3 others
I've found both to be stable.
Initially some S/w didn't like Win 7 64 bit but a lot of the bugs have gone now for me.
I prefer the interface of XP, maybe I'm just used to it, but even after 2 yrs Im not keen on the visuals of 7.
Win 7 does seem to require a much faster processor and much more RAM. Bloatware springs to mind, but it is trying to do a lot more than XP did for me.
I'm not highly technical as far as PC's go, but I'm no beginner. I just use it a lot for work and play.
As far as mobile goes, I've no idea. My phone just makes calls, texts and takes pictures!!!