I have an upgraded version of RC2a with about 20 "essential" contributions installed.
Plus som addons not available in the download area.
Furhter all bugs fixed, known and unknowns. Both catalog and admin are w3c-validated.
Wrt v2.3.1 I doubt that there will be a fully validated release available at all.
Harold have adviced me to stick to my version and only fix the (SEC) and (BUG) in the upgrade.