Thank you. :) I tried to make it a bit more full, since I was late in answering.
In autumn, there will probably be better cards (AMD CEO talked about yearly release of new GFX cards and Nvidia might have 512 Fermi or fermi 2 on the works then). If DX11 isn't a problem for you in the immediate future and framerates are acceptable, I find no reason to buy a new card other then tinkering purposes.
My personal experience with ATI cards and drivers:
History:
In autumn 2008, I was considering a new card between an EVGA 280 (I think it was called black pearl or black something) and a Gainward (Palit) 4870X2 tricooler edition. I bought the tri-cooler edition, made custom profile for silence and had a rock stable setup until I bought the 5870. With the 5870, I got grey screen issues. With lots of swapping out parts and troubleshooting, I could not find out why this happened. It only happened in 3D and only when I had a single screen attached. With double screens, I didn't have issues. Turns out that both my PSU's were failing. One of the PSU's crapped out and took the card with it, while the other was getting unstable (I tested it specifically for that). Weirdly enough, they performed stable with the 4870X2, so the power profile on the 5870 might be too aggressive and failing PSU's might not handle that.
Since the 5870 crashed, I needed to get a new card. As always, I am looking towards offerings from all vendors, since its the products I am interested in and I am vendor neutral that way.
The GTX480 is new and shiny, so the tinker in me wanted to buy that one "to get something new". But, I have invested much time and $$$ to get a quiet PC where I can surf quietly and still have good gaming capabilities. While the GTX480 definitely is a great performer and undoubtedly faster then the 5870, the heat and power would make my system too noisy and I would have to clock it down to get some decent temps and fan speeds. Even then, there is almost no headroom. So, it would probably perform less or the same as a 5870 once I've gotten it to the sound profile I want. I got the Powercolor 5870 PCS+ recommended for my "quiet, but powerful" goals and I must say that it doesn't disappoint. The reference cooler of the 5870 ain't that bad, once you have made a custom profile, since the GPU has low power requirement and heat to begin with. But, this card is a dream in terms of cool and silent. I would not buy it if I was overclocking, due to lack of decent voltage control, but otherwise, its stellar.
In an already silenced system with fans operating at low RPM's, its idles at 33C with 9% fan speed:
The default fan speed is pretty aggressive, so I prefer to use it with MSI Afterburner. Here is a 20 minutes extreme burn test with Afterburner and default speed (60C with 45% fan speed, unnecessary high fan speed). Tested with high rpm on intake fan.:
Here's to show the potential in setting different fan speed. 75C at 25% fan speed, 20 minutes of extreme burn. (tested with high rpm on intake fan)
Needless to say, I achieved my goal of quiet, but powerful build. :rockout
Next, I'll take driver experience indepth, but I have to work a little. :)