Mules just keep on surprising you as well - they've always sounded great with my Marshall, but I've been noodling with an Epi Valve Junior that I'm modding and the clean tone out of the Mules is just gorgeous, been playing jazz progressions and blues all day.
One of the best things about the Mules is the bery definate variation in tone between the bridge/middle/neck selections - some PAF sets I've used didn't really have much to offer in the middle position, whereas the Mules are almost single-coil'ish in the middle position, quite funky with that hollowness to the note.