Zach Levine has an article on the early returns from the 2010 draft class. Well worth a read for the explanations, here's the summary:
Best start (early round pick): Vincent Velasquez
Best start (late round pick): Dan Adamson
Best in flashes: Mike Foltynewicz
Most tantalizing: Tommy Shirley (who is out for the season with a bone bruise on his knee)
Most advanced: Ben Heath