I LOVE my BM hunter! I can't imagine playing another spec.
However, I've been a little disappointed with my one exotic pet I've tried. The Chimera just looses HP too fast! My cat is SOOOO much better at tanking. I hardly EVER have to throw a heal at him, but the chimera needed one every fight.
Also, all the exotic special abilities don't really seems so "special". The only one that is really very interesting is the rhino's, but I really worry about the knockback pushing a mob off a cliff or something, and then having it collect a ton of friends on his way back to the fight.