The 5870 by ATI is the pinnacle of modern video cards. With 1600 Stream processors and a hefty 1GB of GDDR5 video memory, this card is a force to be reckoned with. As a GPGPU programmer, I use many different kinds of cards at work, both ATI and NVidia, and I can without a doubt say that the 5870 wipes the floor with the GTX 480.
Because of issues with the manufacturing process, both ATI and NVidia were not able to fully realize their new product line. For ATI this meant leaving out some of the extra features of the Evergreen, and for NVidia it meant leaving out some streaming processors as well as attempting to fit more onto the card than there should be.
I upgraded from an ATI 4870X2, a card that still ranks highly even though it is the last generation of cards. Although both cards feature the same amount of stream processors, for graphics and compute the 5870 takes home the gold, being not only far more powerful, but also far quieter. My 4870X2 would regularly get to around 90C under load and around 70C idle, which in the summer makes for an unbearable room. The 5870 however idles at around 43C and under load around 70C, a massive improvement over the 4870X2.
I recently had a hard drive die and I believe that heat from my previous card was a primary factor in its untimely demise. I am happy to state that my case temperatures are far cooler with the 5870.
For those who are concerned about power, this card draws far less from the wall under idle due to ATIs downclocking when the card is not in use. This can be turned off but in my opinion is one of the strongpoints of the card.
Now, for the gamers. The 5870 is a beast when it comes to gaming, to get non fluid frame rates on my 4870X2 on Call of Duty: Modern Warfare 2, I was using 2x anti aliasing, high textures, no soften smoke edges, no HDR, etc. With the 5870, I have increased every setting to max and I am still getting better performance than I did with my previous settings and the previous card. I am currently playing the Medal of Honor Beta and this card handles it beautifully.