I've built rpms for and and installed OL 2.4.6 on my Fedora FC6 test/production machine. The rpms were built from a Mandriva cooker srpm built by Buchan Milne, with a slightly adapted spec file, which adaptations I've let Buchan know about.
Experience to date suggests that 2.4.6 is a drop in for the 2.3.39 that it was running, with the exception that a few of the spec file parameters had to be changed for FC6, but more importantly that a couple of the basic ACLs had to be changed: It seems that 2.4 is more picky about ACLs than 2.3.
It's running well for basic user authentication, smtp and IMAP and coping as well as 2.3.39 did. Now I've got it running, I'm looking at the Administrator's Guide for 2.4. This is a fantastic, hugely amended and augmented document in comparison to the 2.3 Admin Guide. I suppose it was Gavin Henry (http://www.suretecsystems.com/) who is responsible for it but can't be sure. Anyway, it's going to cost me a couple of days to go through it and see what more OL 2.4 can mean for my production systems than 2.3.
I trust than Buchan will provide an srpm for Red Hat/CentOS/Fedora people at http://staff.telkomsa.net/packages before long.
Best,
--Tonni