Well, I have mod points, but rather than using them, I'll tell my story.
My wife was losing mail and we couldn't track down the problem. I had server logs showing that some mail was accepted by fm, but then disappeared. After much hair pulling, I put in a support request.
I quickly received four pages of logs showing exactly what happened to the mail in question - from the time it was accepted until it was deleted by an email client.
It turns out that there was a Mac Email client which was set to delete mail coming from sources not in my wife's address book. I thought she was only using the webmail. But every once in awhile she'd start the Mac client and it would reach up and expunge mail from the one or two people who were in the fm address book, but not in the Mac Mail address book. Gone without a trace!
Believe me, this kind of service is worth far more than $20 per year.
As you can see from the thread, these guys build on free software, and give back. I run a number of mail servers myself, but I (and my family) use fm because it would take me man years to add on what these guys offer, to say nothing of admining it all.
I'm always amazed that people are willing to waste dozens, maybe hundreds, of hours just to save $20 per year. I keep trying to get my daughter to use fm, but she'd rather struggle with the spam on the free service I provide her on one of my servers than fork out the $20. Wastes my time, too.