Well, I ended up getting one of those little $30 Little Bear Woolly Mammoth Clones, and it's not too bad in the FX loop of my filter. It's cool if you are in a really heavy band and just wanna leave it on all the time. For me, it's just way too loud to really be usable with the rest of my board. I can dial in my EQ it and blend it with the clean signal in to be sound pretty neat, but when I turn the fuzz off, I have to spend a minute adjusting my amp and filter back to normal settings and whatnot. I can tame the volume with my little BBE Opto-stomp's -15DB switch, but that's too much of a hassle, doesn't help with the dynamics, and I want to use that compressor on my drum samples. Overall, not a bad little toy. It does sound really good, though. Definitely thick, heavy, woolly. It's got plenty of low end, but I don't think the low end is quite as articulate as with the real deal from ZVEX.
It's just so hard to get fuzz to work well with my other effects for bass. I think I'd rather just start with a square wave oscillator and dial in a really aggressive bass sound on my synth than try to work fuzz onto my bass effects.
Also, I'm never really happy with my fuzz tone. I feel like having a nice pre-amp and tube saturation is where it's at. Filter and reverb are the only things I really go to for bass. Delay is nice, but I feel like you miss out on a lot of the subtleties, you can't really appreciate all the nice sounds the bass is making when you have all these repeats. I can make some really cool, heavily modded stuff for solos and always enjoying droning out and self-oscillating, but that tends to really muddy in the mix.
I try to have open mind. I enjoy when people find new ways to make synthesizers and modulate sounds with stompboxes, rack gear, and desktop modules or DIY modular systems or whathaveyou; but I am such a purist when it comes to bass. You can only do so much to the sound before you're taking away from the awesome that you're creating by having the instrument in your hands.