What is the state of the art in (open source) antispam content filtering software? Is SpamAssassin still it? There hasn't been a new SpamAssassin release at all in over a year, and the last major release was nearly 2.5 years ago.

I'm not terribly happy with the performance of SpamAssassin these days (it blocks a lot of spam, but an annoying amount still slips through, 5-10 per day) and am wondering whether there is anything better out there now.

I've read briefly about Dspam, but don't know much about it yet, has anybody used that?

Note that I use SpamAssassin as a MUA delivery content filter (through procmail), and have all the usual MTA-based antispam knobs turned up to 11 in Postfix.