NOTE: The gtx 660m, 650m, 640m, 635m are the NEW 28nm Kepler parts. The gtx 675m, and the 670m are the 40nm Fermi parts. The 640m-LE comes in both flavors. Page 45 MaximumPC Magazine ...July 2012 issue...shud be on newsstands now.
So when considering a laptop...remember that the 28nm parts will suck less battery...and run a LOT cooler ^^