From what little I've read on Grigsby, he sounds like a Brooking-type player in the middle. He sounds like he'd be a good fit.
I think what the Falcons are looking for is someone with good speed (4.6 or under), that is a force against the run, preferably doesn't struggle in traffic like Draft & Brooking have, and can at least be somewhat of a presence in pass coverage.
Another name to keep your eyes on its Clemson's Leroy Hill. He's small (measure 6-0/223 at the Senior Bowl), but if he can put on more weight between now and the Combine and then his pro day, and show some improvement in pass coverage, I think he's got a shot at being a selection by teh Falcons in Round 5 or later. Right now I think omst are considering him a 6th/7th round prospect.
"Vincere scis, Hannibal, victoria uti nescis" -- Maharbal, 216 B.C.E.