He has very very good stuff but not elite stuff in the class of a Ben Sheets curve, a Johan Santana change or a Liriano slider. But then again, only about 1% of pitchers actually do AND are successful with it.
His fastball has great movement and he commands it very well. I heard a lot of comparisons and the one that I feel is the closest is Mike Mussina. Very, very good pitcher but not a totally dominant one.
"Think of how stupid the average person is, and realize half of them are stupider than that." ~George Carlin