I liked it well enough, but I agree with the "bland" criticism. It just felt like they could have had more fun with a concept as outrageous as Abe Lincoln as a vampire-slayer. I went in expecting something either completely awesome or so bad-it's-good.
Instead what I saw was the sort of movie I don't regret seeing, but forget an hour after I watched it. Or would have, if not for such a memorable premise.