I just picked one up from John at wymoreguitars.com (highly recommended, BTW).
Here is my quick review after fiddling with this pedal for a 1/2 hour. First impressions (subject to change, of course).
Pros: I began with all the sample settings as starting points. I enjoyed the Fat Tube setting best, than the Fliptop and SVT.
This pedal is as close to a tube amp as I've heard coming out of any non-tube piece of gear I've tried. The SVT setting is easily identifiable as an original SVT and 8-10s stack sound. I was not able to crank the volume level in my apt. to see if it has that same "sag" at higher volumes, but at moderate levels it seems very, very close. I haven't had much experience playing thru B-15s, so I am not a good judge of how close on it is to those amps, but I think it would have to be at least in the neighborhood. The Fat Tube was my favorite setting. Very meaty and thick sound. It seems like it would cut, but I'd love to hear it in the mix.
I was pleased to find the pedal can drive a power amp, and found that it sounded a tad better direct into the power amp and in the effects loop than in front of my pre/power amp rig. The controls are very sensitive and have a wide range of adjustments. The Mid knob is voiced very well. Unlike some, I've not had a problem with the mid suck of the SABDDI (turn down the low+ highs, and/or use the blend knob), but it is a nice addition.
Cons: I though the high knob could be voiced better. It is more like a presence knob. Would be nice to have a lower tuned high knob also. I am generally not a fan of the more extreme overdriven sounds, that said, I did not like the ones from this pedal. They might be in there with more twiddling, but the ones that I found were not pleasant. The slight over driven sounds (SVT) where very nice however.
Overall, this is a great pedal, and will replace my SABDDI as my backup preamp at a minimum and could be an "always on" effect dependent on the gig.
reference gear: Fender jazzes (flats and rounds), Demeter preamp, QSC PLX power amp, Epi 310UL cab.