So, I bought this pickup seeing the advertised high output and I'm pretty impressed! I think it nails that pop-punk w/ a pick kind of sound that I was looking for. It seems to be well worth the $35 asking price, but time will tell Here's a vid of me covering a Blink-182 song with this pickup. I eq'd the song track to reduce the original bass track.
I've not used any GFS bass pickups, but I have been pretty impressed with their guitar stuff. Especially their Dream 180 humbuckers.