Some information regarding Unity:
* gnome-session - patched with backport which enables session management. Awesome feature, works properly. This is required to launch a session named 'unity' (could be a lot of things, I've decided to name it Unity). Once this session boots there's a small file loaded from /etc/profile.d that sets the env var COMPIZ_CONFIG_PROFILE to the profile I want compiz to run. Currently the compiz profile is also named unity and it's loaded through the .ini backend as suggested by Vincent (Ubuntu uses gconf). This is working properly.
* compiz - I've built compiz from 0.9.4 sources and patched it with 'all' the Ubuntu patches. For Unity I'm not really needing compiz-manager and it should actually be removed because under a normal GNOME2 session it brings problems with compiz 0.9.4 (the interface isn't draw on the screen).
Anyway we can automatize the removal of compiz-manager ? Or what would be the best way to do it?