Both new cards are based on the GF114 and therefore profit from the power optimized chip compared to the older GeForce GTX 485M. Therefore, Nvidia managed to get a higher performance at the same power consumption.
More information and benchmarks can be found on the graphics card pages:
And of couse on the benchmark list and gaming benchmark list.
The three new graphic solutions for laptops will arrive in Clevo based laptops (P170HM3 - 580M, P270WN - 580M SLI), in the Dell Alienware M18x (580M SLI) and the MSI GT780R (570M).