We hate spam at Foliovision. Enough to have written a very effective anti-spam plugin ourselves. Our FV Antispam is on use on more than 4000 websites right now. If you like or use Akismet, FV Antispam works great. It can radically reduce your Akismet costs by cutting down on the amount of requests you send to Automattic, making an agency license go much farther (monthly limit, 100K checks).
FV Antispam also can speed up your site and lower server load as it processes machine spam locally. We also make sure that machine spam goes directly to trash so you don't have to waste time checking it manually (too many comments in a spam folder makes it impossible to evaluate any of them properly).