A few points others may or may not have mentioned that are important:
1. Fermi's polymorph engine handles the tessellation very well, only if it isn't taxed in other heavy shader tasks. This is evident in the Unigine bench that NV themselves release in comparison to a 5870, they ran it at 1920 res, with NO AA and low AF to really put the least strain on the fermi gpu as they can, so its tessellation can be impressive. This is further evident in the 4xAA and 8xAA results, where the 5870 actually equal and beat Fermi, respectively.
2. NV's original clock goals are in the 750mhz range. Now they are settling for 625mhz. The thermals are also very high, with many sources suggesting 280-300W TDP for the 480 (even FUD agrees with this), and 225W for 470. The 470 comes with 2x6pins, thus maxing out at ~225W dead on. The 480 has 1x6 and 1x8 pin, giving it ~300W. There is very little room for OC based on reference boards. Any OC will have to wait for custom boards.
3. VRAM limited benchmarks, at max res and mostly 8xAA, the 5870 1GB start to chug along, as you can see in some min fps. its single digit low, indicating main memory usage. Tone it down to 4xAA, situation will be different (ie. benches available everywhere for 5870 at 4xAA, numbers are good). Ofcourse, the opposite is also true, Fermi handles 8xAA max res better (but not in tessellation scenarios), but realistically, those games aren't at all playable at the low fps regardless. You need a 5970 or CF if you want max eye candy.
4. A 5850 can be had for ~$270. It will nearly always OC to 5870 speeds, in most cases easily reaching 900+ mhz (Mine does 950mhz and stays quiet). Nothing comes close to bang for buck, and if you want more performance, CF 5850 and OC both.