I bought the zoom B2 a couple of years ago for a cheap introduction to pedals for my bass and its pretty impressive for the money. if your wanting just a general multieffects pedal that you can experiment with and gain experience with putting effects on top of one another then this is a good one to choose, it has 20-30 channels (can't remember exactly) that you can program so plenty of space to save effects you like and still create more, plus with another 20-30 pre programmed channels you will probably find something you like that you can tweak to your exact tastes
The only thing I don't like about the Zoom bass pedal is the cheapo plasticity of the case
this sounds like the Zoom B1 which looked pretty..well... nasty, there's no other word for it. the zoom b2 however is a lot lot sturdier and robust.
the only two bad things i could say about the B2 is that
1. there is no clean channel on it so if you want to play clean you actually have to create a channel specifically for it.
2. you need to know about effects and there termanology becuase there are no 'layman' terms for what the effects are (although the instruction are pretty clear)
but other than that its great value for money and with the zoom B2.1 being a little bit more you can have a wah pedal as well.