What I have done is this:
Uninstalled all the 2.7 GPE apps – no loss of data observed
From here
http://linuxtogo.org/~florian/maemo/index.html
Installed all of the Stable Maemo 3.0 (Bora) compatible applications from cobb.uk.net
Installed all of the Stable Maemo 3.0 (Bora) compatible repositories

Application Manager/Check for updates
Update all of the files

The only snag I have hit is that GPE Summary doesn’t seem to want to launch