After installing the mt-blacklist plugin, I did notice a delay in commenting. (I thought it might just be me – since we've been having trouble with our servers anyway) – but it turns out it's not just me. There is a hack on Wizbang that solves this problem [via Jennifer's ETC blog]
While also browsing through ETC – Jennifer's post about James Seng's Bayesian Spam filter reminded me to bring this up into an actual post (it's actually linked in the comments in the Anti-Comment Spam post, and I kept forgetting to highlight it)