One of the most exploited pieces of software in history. I use it on my BSD machines because it's integrated into the OS - which make updating easier.
Of course, if I used postfix, there would be no need to update. :p
Toad, to be honest I can't remember which variant of *BSD you use, but I do know postfix is one of the FreeBSD ports. Postfix can do everything sendmail can, transparently. If you want to run it, I'm sure you can.
Me, I updated right away because I couldn't get postfix running on Fedora Core 4 as you guys may or may not remember. It probably doesn't matter since the MTA doesn't listen for incoming connections, nor does it send mail to anyone outide the computer (ISP won't allow it), it's firewalled by IPTAbles and my router... but still I always patch.