The PFC 01 Compounds (as well as the Hawk HT line) have a very agressive initial bite... not something that's good for us new track drivers as a little tap in a corner may buy you more than you were expecting.
I think I'm going to go w/ a set of Hawk DTC-70 race pads as recommended by Tim over at StopTech. They're designed w/ a very progressive bite, which should be better for learning to brake at the limit with.
Dean's also recommending the R-4 and possibly the R-4E (Endurance) compounds. They're significantly cheaper than the Hawks, but I don't know their availability for the ST-40 StopTech calipers.