After upgrading TortoiseSVN and AnkhSVN to SubVersion 1.5, I set about upgrading the server this morning. The main reason for this is that I wanted to merge a branch back into the trunk using the integrated merge option, and this simply doesn't work with a 1.4x server and repository. Everything needs to be 1.5 for that to work.
We're currently on 1.4.5 ish, from a previous 1-click Windows/Apache setup with some mods for groups authentication.
I just downloaded the 1.50 server Windows binary and it actually now does a nice thing of asking whether you want to use SvnServe or Apache.
I had some issues originally running Apache 2.2 with 1.4, and ended up with Apache 2.0.x but gave the new 1.5 install a go. The following is how I upgraded my install from 1.4x using the same httpd.conf settings from the previous installation (link above).
Upgrading the Server
Upgrading the repository