saas-X is just a snapshot of trunk at a given date. Every month, or two months, we create a new saas-X based on the trunk and we upgrade automatically OpenERP Online users to this branch, so that they can benefit from new features.

There are no difference in terms or bugfixes or features in trunk or saas-X. Trunk is more up-to-date as Saas-X are frozen at a given date. Sometimes, bugs are fixed in saas-X as it has been reported by an OpenERP online user, but then we forward port to trunk.

Yesterday, 6000 OpenERP Online instances have been upgraded to saas-2. So, they can benefit from new features like mass mailing marketing campains.