Lots of interesting points brought up here and some guys have some clear field experience with bears and some are just making judgements of what they have read or think would work well. I think that the big bears both grizzly and browns get a lot of respect from folks, but we tend to put them on a higher pedestal as opposed to where they should be. These things get killed up here every year with calibers of guns of all different types as well as bow and arrow. I think the most accurate statement made so far was by BobinNH he said,

...It gets ugly quick if you don't hit them right. I learned that early....I hit too high. I discovered you can't hit around the edges and get away with it.They must be hit "just so"

Thats the bottom line. These are not ungulates they are predators and lobbing lead/copper via bad angles will get things [bleep] up in a hurry. Theres a lot of hunters out there that truly dont shoot well under pressure, then theres the group that absolutely cant wait for the optimum shot angle and try to compensate that with better bullets. The bottom line is with Bears, all of them, you have to make good shots, and pass on the bad shots. My 9 year old son shot a big black bear this past spring and I was backing him up when he made the shot at 15 yards. This black bear was just about as big as most grizzlies I have seen in our area. The boy made a not so good shot, and I was forced to empty my 338WM from awful angles, half hanging out of a tree, without clear shots but managed to break the bear down and kill him. I clearly agree that there is no worse feeling in the world for a hunter than seeing a big bear shot in anything but vitals. You'll only do it once, that I can assure you.