Beast Mastery is the god spec for levelling. I went Survival at 85+ just because it's impossible to pull aggro from my pet and the serpent sting on Multi Shot is awesome for when i queue dungeons/feel like AoEing.
Grab glyph of misdirect and there'll be no cd on it for when you want to pull big packs etc.
I would give MM a try for leveling until about 70 when you get Serpent Spread for SV.
go MM, because you get aimedshot, because it oneshots mobs :-)
(they may have changed this though, last time I leveld was just a week before addon release)