i had the original Bass-Drive, and it was pretty cool for a 2-channel OD/distortion, i think the current MOSFET versions should be even better (apparently MOSFET is more tube-like)
i also own an Ampeg Scrambler reissue, and to be honest, as a usable bass fx, its a bit of a one trick pony, on the recommended 'Bass Fuzz' setting, its overall effect is kinda like a tidier muff, it should be noted that there is no gain or level controls, so really its a question of balancing the low-response with the output volume, using the two controls: TEXTURE (ie: tone) and BALANCE (ie: clean blend). to use it as a bass fuzz (which is what it is advertised as, a fuzz, not an OD)its quite cool, and if you boost the texture (you will loose lows but will gain general volume) you get a 'wet-sounding' fuzz, not unlike clips of the B:AssMaster i've heard.
also the pedal seems quite responsive to playing dynamics
http://soundclick.com/share?songid=6502055
heres a demo i put together a few months ago
also, ill mention this:
although its definitely not an OD, in a mix, the MXR Bass Blowtorch can do a great Billy Sheehan impression, especially on higher-register notes, its mid-range focus cuts through the mix, and Billy's tone has a great mid-focus, which is why it always pops out.
also in a similar vein, the ashdown James LoMenzo Hyperdrive is apparently the way forward, ive not heard it or used it, but its a mid-range drive/distortion with tonnes of options, and its just had an awesome review in this months Bass Guitar Magazine (british publication)