It's no secret that 4G is a battery hog. Also, GB didn't fully use both cores of the processor, which ICS does along with upclocking a couple hundred MHz. That its also likely to increase power consumption over GB. I have heard many people say the OTA ICS build has much improved battery life vs the earlier leaks, but not sure how it compares on average to GB.
I leave mine plugged in most of the time anyway, so I don't have enough use on battery to know how my life has been from 905, 232, and now to OTA 246.