I don't see any issue with letting glade2 and glade3 coexist for a while.
Space on the Developer Spin LiveCD or the non-live GNOME DVD?
just fear that there may be some issues when using glade3 on glade files that have been produced by glade2.
Would it help to have Glade3 in the Fedora 9 Beta and Release Candidates ISOs in order to get a bit more widespread testing?
Cheerio, Debarshi