I don't think it has to do with AMD's ownership. My former HD4870 was also produced under AMD's ownership and that card was absolutely rockstable and always worked flawless.

It's just the drivers for these cards that plain suck. i kinda regret gettin 2x 5770 instead of another 4870 but it's a done deal now. Let's hope ATI will come up with a driver that will solve all this so we can start enjoying our cards.