Probably also worth noting that until last year, the last few years he hasn't looked all that great.
2004, AA, 1.39 WHIP, 4.02 ERA
2005, AA, 1.41 WHIP, 4.07 ERA
2005 AAA 1.94 WHIP, 8.31 ERA, 0-3.
2006: AAA, 1.23 WHIP, 2.96 ERA.
Last year was his best year in the minors so far, by quite a bit...a lot better than the years before it, and he's going to be 25 on March 24th.