I haven't, as I don't have a tube amp to get the most out of it (I use a Ginger pedal built by the above johnk for any of my ss boost needs). I have owned a couple of other W&C pedals and can vouch for the quality. There are plenty of players around here that swear by the Phat Phuk B, some even saying it should come with all bass purchases
. The "B" model is a version specifically tuned for bass, so I can only assume that means more low end retention. From what I understand, it also boosts the treble a bit for some bite, which I noticed the LPB-1 does when I had one.
You may not get much traffic from owners in this thread, but you can do a search or check out the the Wren and Cuff club thread: Official Wren And Cuff Club