I've used this pedal on one gig with my MM Sterling 4H (BEAD). I usually use a Tech 21 Para Driver DI; so I put both on my board to compare thru the PA (small club w/subs). The Geddy pedal made the low end less full, BUT sat in the mix better than the Para, the Geddy got rid of muddyness; it sounded like a taylored bass tone that sat in the full band mix very well. I admit, I still like the fullness of the Para Drive when alone; but in the mix the Geddy pedal sound best, so I used it. I went out on the other side of the stage to check it when playing a full band song and really liked it. I used a Duncan Studio Compressor before the Geddy pedal with level slightly lower than the bass guitar to hit the Geddy with touch less signal.
Next gig I used a, Fender P-bass build with Jazz neck and single EMG Geezer P, passive (tuned BEAD), used the compressor after the Geddy pedal on this one.
I noticed when using the Geddy pedal we didn't have to make much EQ adjustment on the PA channel. I also think the Geddy pedal works better on the passive bass. May not be a tone you want in the studio, but live it really is easy to EQ a good sound.
I'll agree that it works best with my passive basses. The two I've used it with in an always-on situation are my Rickenbacker 4003w and my vintage SD Curlee bass. If anything, it gives them a very nice, almost cab sim like tone. In fact, I don't even put it on my board when the actives are being played. If I want an overdriven tone with those basses I'll reach for the Darkglass AlphaOmega or a Cog Effects Mini 66.
