Now, these games are no longer a monstrosities that I'm afraid to run at maximum settings anymore. They're quite playable. In fact, apart a couple of moments when performance rapidly drops to a slideshow (some places and after a couple of hours of gameplay), I had no issues performance-wise whatsoever.
I'm fully satisfied by HD5870. Especially now, when it doesn't die on me after a day of work :D It's robust and quiet. The only grief that I have is that I wanted it a year ago, but even now it's a very, very good videocard.