Ok, just noodled around on the Gibby TBird, Eppi VP and the FrankenGoth with the fat shuga pedal.
First observation - the reverb even at max doesn't really do much in the way of creating depth and fullness like it would on a guitar. Turn it on, max it or leave it off, not that noticeable.
Second observation - the overdrive portion of the pedal is very creamy and thick, not harsh or brittle, not really distorted, just ultra thick.
It played well with the Gibby bird but not much more than I could easily get by just tweaking a couple of my parametric tone controls on the Thunderfunk amp. For this bass, not worth the cost of the pedal.
It took my FrankenGoth to a new high. Recall this bass now has Bart classic pups and an Aggie 2 band preamp. It took a gut punch bass tone to a full frontal lethal assault. In essence this is an overdrive pedal for a bass that has overdrive built in. The stack up of gain systems works very nice in this case and creates a super thick, super solid, super loud, super exaggerated deep bass tone that could easily walk all over the entire band. Used carefully for intros and solos it might be a good pedal to have for active basses. Again the reverb portion of the pedal was a non factor, wouldn't even know it was on without listening very carefully.
On the Eppi VP - I was shocked. I expected results close to the Gibby TBird. NOPE. Very similar to the FrankenGoth except a bit more musical and useable. Still nearly the same massive tone as the FrankenGoth except slightly subdued on the bottom end and enhanced on the top. Ultra solid mid range. May be a perfect pedal to leave on all the time in a metal, hard rock setting where overdrive is desired without losing clarity of the notes.
Conclusion - I'm not much of a pedal guy but I could easily see a place for the Fat Shuga with my VP or Goth on a large number of songs. Not so much the standard Gibby bird. The overdrive is the silver bullet in this pedal. Are there other OD pedals that could sound even better with these basses? Probably, but not many if any at this price, especially with the reverb feature and ability to pull double duty with both bass and guitar.