The specs on the mobility 5870 are basically on par with a desktop 4870... which, in a chip that fits into a laptop thermal and power envelope, is freaking amazing.
-The first rumored benchmarks on this pretty baby supposedly put performance at 5770 level in 3DMark scores, which makes sense, because the 4870 performs about the same in 3DMark benchmarks. Overall, this is more like a 4870 in specifications, with the 5770 powersaving features and improved manufacturing process (40m). So, if this was a desktop part, it would be slightly superior to either a 4870 or 5770. For a laptop part, this should be easily superior to the 55nm G92 based Nvidia 280m.
With most gaming titles being multi-platform (read console ports), it should be possible to have a perfect, smooth gaming experience on a laptop now. Of course, if you have about $1700, that is.
-Its good to see Asus in the mix tho, they seem to price their laptops fairly, even if they have high end parts like this. (If Alienware had the first mobility 5870 in a laptop, they'd charge 3k).