I've got a BB2, a Drive Master and a Maxon OD-9 (Tubescreamer).
They're all good for different things:
BB2 - great for a clean boost and lower gain blues/rock. Has quite a "busy" tone but it's full and quite thick sounding. Did a great Angus tone tonight, which surprised me!
Drive Master - superb rock/old metal pedal. Really does sound like a stack at reasonable volume! My favourite pedal to use with my Valve Junior for practice, given the full EQ tweakability. Thin Lizzy in a box.
OD-9 - I use it for solo boosts only, not for a main sound. Superb at what it does - adds mids and volume to fatten out solos. Works well with the Drive Master when the DM is set cleaner than Death Metal ;)