There seems to be a new player in the open-source anti-spam sector

Companies and ISPs that want to stop spam before it hits a user's mailbox may be interested in VA Linux Systems Japan's SMTPGuard, an open-source, anti-spam program for mail servers.
I know there are others but seeming I don't have much experience with any of them and I have a customer looking for a solution,but not on the open-source market (well not for the moment ) , I was searching info about them.

Then I found this article regarding the new open-source anti-spam server software SMTPGuard.

It is supposed to be working kind of different then existing anti-spam solutions in that it :

SMTPGuard collects data only from SMTP sessions rather than examining the text of a message. Thus, it looks at IP (Internet Protocol) addresses, MAIL FROMs, RCPT TOs and their historic frequency. These factors are then given weight points based on user-designated set of rules.
Ok I know that most of the anti-spam solutions go check the content of the message and base their conclusion on the content ... I also know that with one such solution I had to do a lot of configuring and tweaking before it worked good enough to stop most spam.
But I wasn't realy happy with that solution (lucky me it was just a short term contract).

So do you guys and or girls think this new software is on the right track, do you think it might be a good approach or is this all just sugarcoating??

I'd like to hear/see your opinion and maybe any of you specialists can give me some pointers to a good anti-spam solution, being it open-source or not.
Or tell me which (if any) anti-spam solution is used by you or your company and why ?

Hope this isn't asking too much

Thanks in advance