After a quick English class....
First you have to get past the whole QB/OL -- chicken/egg debate. Personally, I think OL is more important.
I love McClain and think he's a can't miss prospect, but when you look at how many holes this team has, you have to also consider value throughout the draft. By the time we pick in the second round, we'd probably be looking at roughly the 7th or 8th OT taken (if not more). You're already looking at "iffy" starting potential at that point (at least for a LT). Meanwhile, we can still probably pick up a very good MLB (possibly even Spikes if we got that lucky, but at worst probably Angerer who was awesome at Iowa).
I'm horrible at watching/judging O-linemen, so I stay out of those debates. But simply put, if the Bills FO thinks they can find a starting LT at the #9, they need to jump on it.