The GF100 focuses much more on dx11 than anything else. In tests of tesselation the 480 showed to be much stronger than the 5870. When dx11 becomes mainstream, the real power of the 480's will be shown and will probably get close to the 5970 in terms of performance. The temps and power are what's seriously preventing me from getting one of these (other than the fact that they're out of stock), I really don't want to get a 480 and a waterblock to cool it and I'm not sure if my psu can power it along with everything else in my rig.
The GTX4xx's have been designed with superior tessellation in mind, however, that increased load is shared with the shader-handling portion of the card. What this means is that tessellation will have a large impact on performance with shaders. The "Heaven" benchmark is almost purely Tesselation so will no doubt give the new Nvidia cards a clear victory. What we need to see is real world performance with tessellation.
Cost, power consumption, heat output...these are all valid reasons to avoid the new Nvidia cards at this time. If you are planning on buying a new GPU in the near future, AMD/ATI offer the best bang for buck. I've been "rocking" a 5870 for about 2 days now and I've been thoroughly enjoying Eyefinity and the great performance I am getting. Even BL works with it!