I have a .416 Remington that I will use on a grizzly and black bear hunt in Alaska in 2011.
I've talked with several folks who have done this hunt. The prime hunting time is right before dark, and so a scope that can operate in low-light situations is critical. Also a scope with an illuminated reticle is a huge advantage, as at that time of the evening your dark colored reticle "dissapears" when it is held up to the black blob of a bear.
I was thinking about getting a Swarovski Z6i 1.7-10x42mm scope.
However I was recommended getting a scope with a larger objective, a Swarovski 2-12x50mm, and then just hunting on the lower magnifications (2x) because most shots are within 100 yards, and many shots within 50 yards. His reasoning is that a larger objective will be better in these low light conditions.