NEATO  FYI, Em@ailCRX, a spam filtering app developed by the same developer, has the equivalent of Sp@mX integrated into it. I can thoroughly recommend Em@ilCRX. This app filters based on authorized countries, friends list, various email validation criteria and routing, plus simple spam reporting a la Sp@mX.  
(Version 4.3.1)

VELGOR  Finally a Universal Binary. Runs beautifully now, and truly makes an impact on spam.  
(Version 4.3.0)

RIKG  After a slight delay in receiving the registration code I can now confirm that this program is up and running and is so far amazing. Good work Jeff!  
(Version 4.2.9)

RIKG  I would steer clear of this program. I purchased the software a month ago and am still waiting for the authorisation keys despite a couple of emails to Jeff. Shame - I've heard so many good things about it but I guess Im not going to get to try it!  
(Version 4.2.9)

LEOOFBORG  Agreed with the anon poster below. 'Sp@mXUser' is probably a Spammer.

Established ISPs score spam by user complaint. If the users don't complain then the spam cannot be acted upon.

The only people who would complain about this software and its approach don't understand it.. or understand it all too well.  
(Version 4.2.8)

ANONYMOUS  I checked Comcast's policy on reporting spam and the comment below is total bunk. They encourage reporting spam and give specific instructions for doing so.  
(Version 4.2.6)

SP@MXUSER  Support for this program is at best poor, developer promisses to fix problems but doesn't. ISP's concider this spamming, on Comcast you can and will be shut down if you send more than a given amount of spam reports in a 24 hour time frame, counters have been requested and promissed but alas nothing  
(Version 4.2.6)

MLOWE969  What can I say? This product kicks ass. I downloaded it, bought it, used it, and reported over 200 emails in a single stroke. VERY easy to use. I'm starting to get replies from ISPs. I only wish everyone would make such useful software for this reasonable price.  
(Version 4.2.5)

LEO OF BORG  Oliver, you make some assumptions.

The fact of the matter is that most users DON'T report spam at all, so any tool where the users CAN and DO is appreciated by the ISP.

Most ISPs don't act on one report, but on a number of reports in batch. The more reports, the more serious the spam.

I used to work at an ISP -- we would use 'Elm' and cull from the main abuse inbox. I would tag and take 500 emails with the same subject, examine a couple reports, deal with the Spammer, and then send 'ThankYous' to the other 498 reports. False positives I would either ignore as a 'slip of the keys' or email the user our 'are you sure this is spam' template.

Even 10 years later, I see the same modus operandi.

Tip to Sp@mX users: DO NOT CHANGE THE SUBJECT of your reports!

If ISPs are now 'scoring' Spam via database and regex it will be based on the subject of the original spam.. and don't worry about a couple false positives as they will not be acting on ONE report.   
(Version 4.2.4)

OLIVER BREIDENBACH  Although the developer claims the higher moral ground for this software, it actually does little to help fight the spam pest. It massively spams abuse contacts and government authorities, which in return will only disregard any of the many so called "Spam Abuse Complaints".

The fact of the matter is, that no spammer will be stopped by overreporting them. In the long run, the only way to stop spam is the widespread use of PKIs and Trusted Certificates and mail servers who can implement policies based on the signatures and certificates of the mail they receive.

Also users should be aware that the software sometimes creates false reports. Falsely accusing someone of criminal conduct is libel and can have as serious consequences as spamming.  
(Version 4.2.4)