I had a few bear run-ins while on the middle prong (LPR) last year. They were scraggly, with the exception of one mama and cub... but don't worry too much about bears, they're timid and shy. They'll usually go the other way before you do. If you run into a cub, though... best to go the other way yourself.
On a side note, I've seen a huge grizzly dropped in mid charge with the spray ... well, OK, it was on a video in Cody, WYO, but I saw it! I'd say it'll do the trick on just about anything (even the people singing and talking loudly!).