I just installed Nucleus 3.0RC and moved my setup from 2.5CVS. It goes relative smooth, but some skin, namely RSS* somehow no longer works.... going to fixed it later.

The steps I did it:
1 - download, install in www directory
2 - copy config.php from old setup
3 - copy all plugins from old setup
4 - copy all media from old setup
5 - copy all custom skins fro, old setup
6 - remove install.*
7 - chmod ugo-w config.php

Update:
- Also copied additemform.template for NP_NotifyMe

Still not working:
- RSS2 feed (a bug in skin??) It's a bug in Rss2 skin...