He will either be better than Mark Prior was last season, or he'll be worse than Al Leiter was last season. Anything in between is also possible.
For the record, I think he'll be a top 5 or 6 pitcher, maybe even top three, but I'm sure many would advise against drafting him. Yahoo just put out a press clipping about him today, in which they said the reports are that he has looked "dominant" this Spring. They even went as far as to say that they are comfortable calling him the best pitcher in the NL again.
That's maybe a bit too much for me, but I think he's worth a gamble maybe even as high as round 2. ESPN has him ranked 13th overall among all players and 2nd among pitchers. If you're a gambling man, he's a high risk, but VERY high reward pick.