I've seen a few get through as well, mostly relatively innocuous stuff. In a couple of cases, it was a text-only email with a very bland subject line, a series of nonsense words or strings of random characters, and a single URL. There wasn't much else for the filter to go on, so until that source hits Barracuda's reputation filter (which it might, assuming the sites contributing to that are getting the same thing), it's hard to catch. Some of that stuff is currently only scoring a .8 or so (on a scale of 0 to 10), and looking at the messages, there's nothing hugely obvious about them to latch onto.
On the plus side, I haven't had to re-create my 40+ item "allowed" list that I needed with M+Guardian to avoid having it whack mailing list traffic that I actually want.
You can change your individual spam preferences if you go to http://spam.drew.edu
and look under preferences. We currently have a system default score of "3.5" for spam. If you make that number lower, it'll be more aggressive when filtering your email, but you're likely to get more false positives and you'll have to really check the quarantine. If that's OK, or you don't care if you miss a few mail messages here and there, you can set the number lower. I wouldn't set it too low at this point, though, you're likely to suddenly get a ton of mail blocked.