Last year, in the face of a weak staff, the Yankees did nothing. The result was pretty predictable, even if the details (Mussina was terrific, the rookies, not so much) were not.
Unfortunately, they did not make the same mistake this year. Like everyone else, I think Sabathia's great. Burnett is good when healthy, although it's worth noting that he has a five year deal and has reached 200 innings twice in the last five years, somewhat like some of their previous signings. (Sorry, Schlamp.)
But all in all a huge step up for them. They went from a rotation of Mussina, Pettitte, Wang, and then assorted rookies and castoffs to Sabathia (a clear #1), Burnett (#2, potentially a #1 when healthy), Wang (a #3), maybe Pettitte (?), then the rookies. I think it's fair to say that Sidney Ponson won't get another 15 starts next year.