Very Comfortable and I've probably had 25+ pounds in mine, short hike with steaks and beer and all that. Comparing it to my Vapor Trail which would handle 35 lbs., I say definitely, but I think that would be about the max. I will say that I like it a lot for winter, group/fun hikes, etc., but I wish I'd got the Gorilla because it's a little more room than I need; but it does cinch down well and is never floppy even with a lite load. The Gorilla is only 2 oz. less though, so probably not too much to cry about. I think the consensus is that 35 lbs. is about the max, and it would always be preferred for shorter durations/distances.
Edit, it will definitlely fit a bear vault in either direction, vertical or horizontal.