I leveled a Bst/Dru very fast to 61/60.
Features:
Dots, nukes, snare, root, slow, haste, pets, ports, heals, hp buffs, mana and health regen buffs, resists, damage shields.
Many times, having my druid do crowd control through snares+roots saved my life. Ports (including succor/evac) are forever handy, as are the sow that actually come from both classes. The bst being able to both slow and haste make the mobs rather easy. Health and mana regen make down time next to nothing. Many times, during bad pulls, I have stuck the druid pet on a mob, bst pet on a mob, kept the bst himself tanking a mob, and the druid keeping the other mobs rooted and doted.
There are plenty of other good combos, classic war/cleric or mnk/shm are both fine combos. The war/cleric combo lacks little CC, and the mnk/shm combo only lacks snare/ports. I personally like to have slow/haste and heals when I'm fighting, although as you can see other combos that lack these are effective as well.