Hi Naim, I have a pair installed in my J Bass with the Neodymium magnets and they sound great and do have much more output than the stock chinese kit ones. They stand quite tall and I had to chisel out a bit in the PUP cavities to make them fit low enough under the strings plus the screw lugs are in a slightly different position that requires that part of the body to be enlarged also.
The screws can be adjusted a little bit but not enough to truly make much difference. On one of mine I accidently screwed a pole in too deep and the screw fell down inside??? Ended up removing the PUP, took off the cover, and retrieved the screw which was then fed delicately back in place from the top with cover already in place.
Tend to think they serve more of a decorative function than anything else. Unlike on a Humbucker where raising or lowering the screw poles can help to shape your sound to a certain degree.
Most guys seem to install Toneriders which have the traditional fixed pole pieces.
About 35 years ago I dropped a cream Di Marzio Bridge J PUP in an Ibanez P J hybrid copy which had the allen key adjustable poles and they do work properly. Here is a shot of what they currently offer plus the hyperlink....
http://www.dimarzio.com/node/2126
Cheers, Waz
Here is the link to my sound demo video ...