I have one in my Warmoth Funk Machine (tried to get as close to the Jamerson formula as possible, except for the active option of course!).
It sounds great, lots of sonic options and you still keep the passive P sound if you don't activate the electronics by pulling up the volume knob.
Since it was my build, I also made a hole in the pickguard and installed the LED.
I had to route the control cavity slightly to fit the preamp, but I guess that would vary from bass to bass.
It's designed to fit in a vintage P-bass, so probably the Warmoth has a slightly smaller control cavity.
I don't know how the rechargeable battery will hold up, but after 4 years it still works fine... wish I could say that about my iPhone!!!
Here's a picture of it charging: the LED is green, sign that it is fully charged.