I see people saying that it doesn't have switchable graphics but still manages to get about 4 hours on internet browsing. The Sandy Bridge quads are generally a lot better than the old Clarksfield ones in terms of battery life. The quads also turbo up to the same speeds as the duals when fewer cores are in use.
Battery life is only part of why you want switchable graphics with Sandy Bridge. You can't use any of the media features, in particular the Quick Sync
transcoding engine, when you're on a discrete GPU so you need a way to switch between them if you want to use them.
As I mentioned earlier, the thing with the Clarksfields was they had relatively anaemic base clocks, 1.6GHz or 1.73 for the 720QM or 740QM most of the cheaper machines had. Sure, they Turbo'd out to between 2.4 and 2.93GHz, but if you were doing that a lot then you may as well have bought an i5 for less money since you were paying the premium for the quad only to have it spend most of its time as a single or dual core. Sandy Bridge is better here with 2.0GHz being the minimum base clock on the quads which isn't entirely terrible compared with the dual cores. The range of turbo modes is better too: 6/7/8/9 for 4/3/2/1 core operation in this case instead of only 1/1/6/9 for its predecessor. I still don't think the quads are worth any kind of premium over the duals, but for USD$899 this machine is a steal, quad core and all.