This article in the Tribune-Star is kinda interesting. It goes along with my contention that the difference between I-A and I-AA has closed recently (for the FCS playoff teams anyway). In I-A, the BCS and the non-BCS teams seem to be separating somewhat.
Key Quote:"Well, I-AA [FCS teams] is a little bit different. The difference between I-AA and I-A, or whatever they call it these days, is not as great as the jump from [Divisions] II or III, for example, to the NFL. It’s just not. And you see more I-AA guys come in and play relatively soon,” he said."
In Matty Vautour's Hampshire Gazette Blog, he mentions this site, which is a rating site similar to Keeper's. It has some errors on the I-AA level.