In general, the admin area was not displaying error messages that originated from data managers, and submissions were not preserved in the form reload (except areas and prefixes which were preserved). Further, for areas and prefixes, the overlays would become broken after a failed submission, due to a breaking change during RC that provided instance support for overlays - a change that was not actually applied to admin overlays at that time.
Both issues are fixed in the next release for all the admin panels I know of that accept admin input and pass through a DM. Some admin panels that pass through a DM already had error checking outside the DM, such as moderator and user mask panels, thus there should be no need to add DM error handling for these panels.