I'd like to say it went without a hitch but that would be lying. I had a bit of a problem with permissions, htaccess files and ftp weirdness. Once that was all sorted EE 1.3 is now up and running.
Improvements are mainly in the backend with a redesigned control panel. Pmachine has also launched a forum module to slot in with this release which looks like a solid product which fully integrates with all of EE's functionality.
Update: Make sure you dump your cache otherwise, like me, you'll wonder why there are so many damn 404's on this site!