Procmail is the kind of thing which just works. I have been using procmail for some time and I have slowly come to realize its capabilities as not just a mail filter, but to run arbitrary commands like notifications(libnotify ones), lbdb addition, date based partition of mails (very useful) as well.
Regarding the discussion regarding procmailrc and whether it is programming or not, I certainly don't think an average computer user would consider it simple. Only people who have written lightweight RE before and are willing to learn more in that, come forward to use this. So, I don't think procmail is targetted at a normal users, but at people who may like advanced customization, and/or email providers.