The 480w thing is to prevent people from using **** power supplies with it.
3 rungs for each, and about the same clockspeed for both the ATI and nVidia. The x800 XT has 16 pipes, x800 Pro has 12, x800 has 8. Meanwhile, the 6800U has 16, 6800 has 12, 6800 XT will most likely have 8. Figure the prices to be 4-500, 250-300, and 150-200. About a 500 MHz clockspeed for both high ends at most. Similar performance. nVidia will have PS3.0, while the R420 has only PS2.0. ATI will still have the advantage of TruForm or whatever it is. Both high-end variants will require 2 molex connectors until the PEG variants come out, when they'll switch to 1. The performance mainstream and mainstream variants will have 1 molex connector, probably won't require that on the PEG variant.
And as always, never buy the bleeding edge card unless you're the kind of guy who would buy a Prometia or a TEC waterblock. The performance mainstream has a far better cost/performance ratio.