as mentioned above, Buchholz is certainly one of, if not the best, pitching prospect currently in the minors. He dominated AA with numbers extremely similar to Phillip Hughes, and a better era. He has 4 very good pitches (fastball, change, curve, and slider). A testmanent to the quality and command of his secondary pitches is the debate over which is the best. I've read many different sources claiming his change, his curve, and slider are his best pitch. He has a good fastball, he sits in the lower 90s but can get up to the mid 90s. However, his largest issue throughout his minor league career has been his struggles with fastball command.
He certainly profiles as a true ace, especially if he can improve his FB command.
AA era: 1.77 ip: 86.2 h: 55 r:18 er: 17 hr: 4 BB: 22 SO: 116 GO/AO: 0.95
AAA era" 3.26ip: 30.1 23 h: 13 r:11 er: 5 hr:5 BB:8 SO: 48 GO/AO: 1.65
If he has all his stuff working I think he's definitely succeed at the moment and be a force in the majors. He has fantastic stuff and command of his breaking pitches. If his FB command is shaky he may be prone to giving up a few HRs, but as you can see from his current AAA numbers, he doesn't allow many people on base in the first place, so the HRs wont hurt as much.
Anyway, I would read this break down of Buchholz (and Joba Chamberlain) to get a better understanding. http://minorleagueball.com/story/2007/8/14/13058/6308
Fantasy wise - i picked Buchholz up since he has the ability to be an immediate impact player. However, unless Lester continues to pitch poorly, there really isn't an opening in the rotation for Buchholz, other than this possible friday start.