I welcome the new battery capacity in that it facilitates using all the camera features as conveniently needed without playing scrimp and save, hoping the battery(ies) last until a suitable time to recharge them. Having to skimp on chimping, Live View, etc. diminishes the clarity over what you are doing/did and the general joy and luxury of the camera. High performance, high efficiency and a commensurate fuel tank, that's the Joy of Driving! Filling at least 2 8GB cards without thinking about letting off the gas for a tank full lets you keep your attention on your photography without the distraction of the fuel gauge.
That said, I can't remember emptying both batteries in the 5D grip before a convenient time to recharge them, or even need to drop in the spare pair I usually carry underway. Only danger with the 5D2 is forgetting all about charging the batteries.