i put some thoughts in the description.
long story short:
this is an exceptionally close copy to the mutron III bubble funk sound. I've tried an awful lot of the "copies," and this one really is as good as it gets. it's funky, it's useable, it's a modern pedal (power supply, bypass, size, intuitive controls) and i could see a lot of people dumping their q trons, MXR filters, and so on for this.
the downsides:
a little volume loss. Huge bummer for me. In my experience, a filter should be louder (if not much louder!) than the bypass signal. There is no subtle way I enjoy using these units. when I stomp on that switch, I want to destroy my speakers, cut through the mix, and seriously bring the funk, as if my name is "bootsy baba!"
So, i think for my personal filter needs i'm going back to a vintage DOD since mutron III units seem to be going for $800 or so now.
I don't think everyone would feel as I do about the volume, many if not most players would either disagree about it or not notice/care. but, it's what I hear. at least I'm aware that i know my needs are maybe a little too specific.
not that any of us care, but if I was a guitar player looking to do the jerry garcia stuff, this would 100% be a gift from the filter gods.