Well, count me in among those who've replaced their stock MIM Jazz p'ups with the DiMarzio DP123 p'ups, and are VERY HAPPY THEY DID!
I have a MIM '62 Reissue that I picked up virtually new from a guy on Ebay. Overall, I pretty much liked the bass, at least for the money I paid. But, I never could get a frickin' tone out of the p'ups that I liked. They always seemed unfocused and "cloudy" sounding. Not exactly muddy per se, but just undefined and unclear. My drummer and guitarist also both complained that they just didn't have any balls, which I agreed with.
Well, I finally bit the bullet, and ordered a set of DiMarzio DP123's from Steve's Music Center up in Rock Hill, NY (I'm near Tampa, FL).
http://www.stevesmusiccenter.com/DimarzioDP123.html
Steve is GREAT! I ordered these babies Wednesday afternoon, and they arrived Priority mail TODAY (Friday) at noon. Not sure how they did that, but if it had been UPS, I'd be waiting until Tuesday. Steve also has the best price of anyone.
I just put them in, adjusted the setup, pole pieces, etc. WOW!

Wish I hadn't waited a year to do this, because now, my bass sounds PHAT!
Big thanks to all those who added good reviews of these p'ups, and to Smash's "J" pickup comparison sticky.
This forum kicks arse...
