I have 1 of the ZVex Super Duper 2-in-1 double boost pedals and have mixed views on it.
I bought it almost 3 years ago while I was in New York, and within 2 months, 1 of the switches had gone faulty and wouldn't work. I posted on the ZVex forum about it and Zach himself took my address and sent me 2 new switches free of charge so that I could fix the pedal and still have 1 as a spare. That's good customer service in my book :)
As a boost pedal, it can be very good or very bad. I can try it on some amps and it'll sound great, while on others it'll sound like cr@p. This isn't something I've found with other boost pedals I've tried though.
I've used a Fuzz Factory for a bit, but couldn't settle on a general fuzz tone I actually liked. It's great for that wall of noise/Muse thing, but other than that, it's not for me.
I tried 1 of those Wah Probes too and that was a cool pedal. I'm not sure I'd take 1 over a traditional wah though.