Yeah the other classic problem with "Orthogonal Persistence" is that it becomes nearly impossible to upgrade your software. All your existing data is locked to

Yeah the other classic problem with "Orthogonal Persistence" is that it becomes nearly impossible to upgrade your software. All your existing data is locked to the old version forever (or until some sort of "migration" can be performed -- which requires a way to dump the data, which you may or may not have).