I'd say Vista is more stable than XP, but I don't know about XP SP2, I found with SP2 it was very stable. With Vista I've not noticed a difference when installing SP1, except for a couple of things that refuse to run without it.
As for compatibility, it's all the expectation of a 100% compatible system and I've found more things than I imagined in Vista work. (After hearing cries of 'Vista isn't very compatible) The only thing I've wanted to run that wouldn't is Summoner, stuff like Final Fantasy VIII runs swimmingly still (just a little tweaking - very little) Though my only complaints are that a couple of fairly recent 3D programs like to crash - like the demo of Cinema 4D 10, since I've downloaded the demo of C4D 11, no crashes, so it may be worth purchasing.
I am pleased with Vista, considering I was expecting a pile of dog-poo when it was released and a lot of stress, I felt better when people told me it wasn't so bad and so far, stress free - my first experiences when migrating from 98 to XP and after 3 years of using it, stress. After SP2 I had no problems.
But I still hear complaints from other people and other experiences, so I imagine Vista still needs more work and hopefully that's what MS rectifies with Windows 7...hopefully upgrades will be cheap.
With the copying each other argument - good ideas are good ideas, innovation is innovation, I think if more people shared ideas, then more users/clients/customers will have a better experience with what they choose. If Microsoft copy apple or Linux, then that's because they had a good idea, likewise if Apple or a Linux distro copies MS.
--The hatred of those who harbour such ill feelings as, "He reviled me, assaulted me, vanquished me and robbed me," is never appeased.--
