I bought one of these to replace the 512mb graphics card which came with my PC as it wasn't able to cope with newer (and quite a few older) games.
I'm very glad I did, it really has given my PC a new lease of life.
Prevously my Windows Experience Index was 3.4 (3.4 for aero graphics, 3.8 for gaming graphics) now the Windows Experience Index is 7.0 for aero graphics, 7.0 for gaming graphics.
My computer will now run just about anything I throw at it, Assassins Creed with all the graphics effects on max, Bioshock, full on, no problem, Half-Life 2 looks gorgeous and plays just great. My PC now no longer overheats when I try to play a decent game, and the card is more or less silent (plus it proports to having a "dust proof fan" - looking at the blackened, filthy card I took out, I hope it lives up to the hype).
My only quibble is that it took me a while to get the software properly installed - more specifically catalyst doesn't seem to work correctly, although the card works flawlessly. However I suspect that might be something to do with the OS (Windows 7 32 bit) and doesn't affect my gaming one bit.
All in all a really good card, good enough for your average (or above average) gamer on a bit of a budget.