We were camping at a Yellowstone campground when a bison decided to take its morning stroll through it when everyone was still there. We just remained very still and let it go where it wanted and it passed through. Upclose, those things are huge. You would not want to mess with one.
Yes they are. You ought to see elk up close once too; had the opportunity once in central Pennsylvania, video cam in hand - awesome creatures ... I took the hint when the bull elk snorted, stomped and mock-charged me after following them for two miles in the forest.