No he hasn't.
Last year was his worst year since 2004 -- his last in the American League.
These are his numbers in his five years in the National League:
14-12 W-L (on average)
3.79 ERA
1.28 WHIP
112 ERA+
209 IP
Take out 2009, and his numbers look even better:
14-12 W-L
3.59...