Ken,

Porcupine Tree (with Gavin Harrison on drums) has a lot of unusual time signature changes. I have been studying a lot of Gavin's transcribed drum parts from Procupine Tree and I have to say it is a little overwhelming for the average drummer. That's probably why King Crimson used Gavin on their tour last year. BTW, Robert Fripp has asked Steven Wilson (Porcupine Tree) to remix some of King Crimson's albums to 5.1 surround. Should be interesting.