I got these for my 5 string converted P-bass, mainly because of the 'rail type' pole pieces. With conventional P-bass pickups I always have had an issue with uneven sound level between the strings; B was loud, E was not, A was louder than E.
With the DP127 that problem is resolved, all strings have even level, On the bargain I get a fuller sound on the D and G than with the stock -78 pups.
Since they are humbuckers they are not as bright as single coils so you'd better go for 500 K potentiometers. The 127s are very dynamic and responsive to how hard you hit it. The sound is raw and they have a very high output and a remarkable sustain. I'ts almost like a bit of an overdrive character to them so if you're into good times rock'n roll or some undefined vintage sound you are spot on. If you are into sweet tone, Jaco style, look elsewhere.
The only downside (there's always some) is that I kind of miss some of the original P tone in the originals or Duncan QPs. As always, you gain at one end and lose on the other.