Just got a great testimonial from Kristie MacLaughlin:
I started getting hit with spam about two weeks ago, and was horrifed to watch it grow exponentially by the hour. I have my comments forwarded to my Blackberry, and it almost shut down my service! I found out about Akismet from a friend, and installed it immediately.
I cannot believe the difference! In two weeks, it was caught over 4000 spam comments! It is absolutely amazing. I cannot thank you enough for making this service available. Spam almost caused me to shut down my blog, but now, I can express myself again without having to spend most of my blogging time deleting spam.
I love Akismet! I will recommend it to EVERYONE I know.
Kristie, it’s our pleasure. Thanks for your kind words.
Akismet 
I agree with Kristie about Akismet 199%.
And is the #1 deterrent against comment spam.
I can confirm that Akismet works just great. During last 6 months only (1) one spam-comment made trough to my blog. This one comment was in Estonian language and posted by real human.
Yes, excellent work. Akismet will hopefully do for blogs what Spamassassin has done for email. Only with something like Akismet will public comments ever be possible at all. Requiring folks to login to post comments is a great way for tight community sites to eliminate spam, but for blogs oriented toward the general public, there has been no real solution. Captcha is OK, but spammers are even building workarounds for that now.
Here’s a review I wrote recently of the Drupal Akismet module and the Akismet service in general:
http://devbee.com/akismet_howto
I have a website that I had to take down at one point because of the spam. Think over 1000 spam comments a day. I’ve since discovered Akismet, and use it on all my sites that allow users to post comments, its a life saver. Even better is that now I don’t have to use some annoying anti-bot captcha or some obscure question such as what is the color of the grass that grows in Sweden to prevent some hack from trying to spam my blog and scare away my visitors.
I was getting creamed by Poker web sites, drug sites and ring tones. Since installing Akismet, every single comment spam has been eliminated, nearly a thousand so far. It’s never made a mistake.
I was able to turn off automatic moderation.
Yes Virginia, there is a Santa Claus.
I was running a spam-word blocker that was getting pretty long; I had to maintain it manually and I’d still I’d get spam. Then the spam suddenly escalated — I was getting battered by a dozen or so spam comments at a time several times a day.
Two days ago, I upgraded to WordPress 2.0.5, turned on the “Blacklist comments from open and insecure proxies” option and installed Akismet. Since then, a couple of hundred spams have been caught, three were held in the moderation cue, and no legitimate comments were held. What a relief! I’m hoping to be able to turn off comment moderation soon.
I want to thank you, Matt, for this.
Yea buddy, this product works most sweetly. We were about to through in the towel, the SPAM was getting absurd at one point seemily 10 to 12 an hour. Took a few days off and when I returned it took me hours to sort through legitimate comments from the SPAM.
I installed Akismet as a last resort before I pulled the plug. This sucker has worked famously. I have not even had a false detection yet. Killer product guys! keep up the excellent work. There’ll be a little something in your donation plate from us happy users.