That was exacly my point (that including org.hibernate is currently a no-no), but I want to document the possible solutions and workarounds on our side, otherwise it's hard to get a clear picture.
I am also working on adding Spring 3 with Hibernate 4 (initially, via Snowdrop), but ideally migrating an application that previously relied on finding Hibernate 3 on the server side should be as simple as possible (and it is possible), and one of the solutions listed above (Hib 3 module for example) would be a pretty fast way to get things done.
And what Scott suggests would be very cool indeed.