I just wired a set of Basslines Quarter Pounds into my '06 MIA Jazz V last weekend! I was a little worried about messing with the mojo of the bass and losing "that jazz bass sound" but they sound pretty awesome. Same great sound but with a warmer, wider low end and a bit higher output. I grabbed a couple screen shots from recordings I did with stock pickups vs. the Basslines, check them out below.
Looks like similar high end (and sounds like it to my ears), but the Basslines seem to have better frequency response in the lows. It's not boomy by any means, just more... present. The B-string seems to be more present as well. It wasn't bad before, but always struck me as a little thin. It sounds quite a bit better with the Basslines! Overall, the Basslines are warmer, but they have a touch more growl at the same time, depending on how much you dig in.
A pretty good upgrade, IMO!
5sg.
Here's the stock Fender pickups:
and here's with the Basslines!