The server here has been upgraded from 10.4 to 10.4.5. I was a little apprehensive about this update as I didn't have a chance to test prior to performing it, but everything went well, Postfix kept chugging, web services uninterrupted, other miscellaneous non-standard compiled code went well. Looks like Apple didn't stomp on anything that I'd upgraded. ;)
The big hangup was an issue with Carbon Copy Cloner, under 10.4, it wasn't able to clone my drive due to an authentication issue, normally I'd clone my drive and test out the upgrade first, so I just had to chance it. The main reason I needed to upgrade was 10.4 apparently had some issue that would keep log files from rotating properly, and possibly other scheduled tasks from running, so it was high time to get that issue fixed.