Tim had a set of unpotted Mules in a Les Paul at LGS, into several amps, 2 Zakk Wyldes, 2 different H&K (one was the Alex Lifeson model), an Engl and a Framus. No one at the show had squeal problems (and the amps were being driven - we also had Keely modded SD-1's in front of them).
Tim suggested the unpotted - he thinks it gives a more vintage tone and I have to agree. I was comparing with a real PAF (which is obviously unpotted), and the sound is really close, though the BK's are more open. Since I was putting them into a 335 and wanted to keep the semi-accoustic tone, the unpotted seemed like a great idea too. For blues and classic rock, I think they give a great sound.