I've been finding out more and doing more...
First off, I have installed EmailWhitelister, an anti-spam plugin that allows you to instantly approve certain comments based on their emails.
Second, I have discovered that the reason the antispam plugins included with MT 3.2 seemed to be fairly lame is because they have very limited defaults. To solve this, go to the menu for your weblog, click Settings, click Plugins, and edit the settings for various plugins.
Given the latest raft of spam, I recommend adding
/ionamin/i
/online-?casino/i
/texas-?holdem/i
/poker ?games/i
to the Spam Lookup Keyword Filter
Thirdly, I have installed "Real Comment Throttle". This plugin simply refuses to accept more than the number of comments you specify, per hour and per day. I've set it to 10 per hour, 100 per day.
Note that this is comments per weblog (so all weblogs are allowed 10 per hour) but the configuration values are set on a per-site basis (we can't give one weblog 5 and another 50). So if you get "wildly popular" as the author says, let me know.
Last, I am personally working my way through the instructions for turning on TypeKey authentication. Woo-eee this is complex!
Feel free to do this yourself.