I finally get the front brakes sorted out (TSW BDM kit, BTSSB), put carbotech XP10's on the rears, and it looks (and sounds) like the rear calipers are binding a bit (especially on the passenger rear). I haven't started messing with it yet; thought I'd get some input from those of you who know better. Figured I'd try cleaning the piston up a bit. Any thoughts? Basically I can hear the rears squealing at relatively low speeds; I can tap the brakes to make it go away, but eventually it comes back. The rear pads are just (barely) rubbing the rotor, enough to squeal, and you can definitely feel resistance when you try to spin the rear wheel with the car up on jacks.
This hasn't happened on my MINI yet, but it happens on my old Miata sometimes (it has very similar rear calipers). On that car, it's always the slide pins that need some cleaning and lube.
Another common problem on the rears that can cause this is not getting the brake pad retainer wires "snapped" onto the piston properly - they can be tricky sometimes.