I'm a big big fan of percentile based skills and powers. It just seems so logical to me.
I had forgotten that FASA's old games were also percentile based, so I'm now borrowing a metric ton of FASA Star Trek game books from a friend who has a real nice collection, and I'm scanning them all and making them into PDFs so I can have my own copies of the books. Once I get the Star Trek books scanned, I'm going to try and fire-up a pbp Star Trek game!