I've recently switched my personal site from qmail to Postfix and had very little trouble doing so. Installing one Postfix RPM easier than the fairly involved process of installing qmail.
Now that Postfix is the default MTA with Fedora and OS X.3 it seems like it might be fairly sensible to at least offer it as an option. Configuring Spamassassin and RBL was also much easier than with qmail (which was the main reason I switched).
