There's plenty of evidence that they're fake. Its all a matter of whether one finds that evidence credible or not. Personally, I think the fact that I can (and have) make an exact copy of it using my MS word at default settings, among other issues, is pretty damning, at least to me. Equally damaging is the fact that everyone who knew Killian first hand and are some way tied to this story appear to be denying their authenticity. Its not a closed-case just yet, but to this point, I'm fairly convinced that they are fake.
My gut feeling on it is that this was cooked up by some low-level DNC staffer (with some pretty marginal forgery skills, I might add) who thought he/she/it would be doing the party a big favor. I actually don't hold it against the Kerry campaign or the DNC for that reason (I haven't seen any evidence yet that anyone at the top was involved), but I suspect it will hurt them.