I've had one for about a week now and I'm really digging it. It can sound really thin and spitty as dannybuoy says, but you can definitely fatten it up keeping the notch controls < noon. It's got a great range of sounds but don't expect anything clean out of this guy. It goes from 10-20, rather than 0-10 if that makes any sense.
The 'more heavy' feature only activates if the main pedal is engaged, which was somewhat disappointing...
You can totally get close to the sound Al Cisneros has on the last Om record if thats your style.
All in all a good pedal. Alan was great to deal with and shipping was a breeze. I'd recommend it.