Users can check changes into the repository while modeling without freezing the changes and updating the version.
Other users can then merge those changes back into their working copies by right-clicking on the model and selecting 'Update from Repository...', then selectively applying the repository changes into their model using merge/compare.
This allows WIP changes to be propagated back to other users when modeling concurrently.
The stop-lighting features in the model browser also provide an indication to the users if their model is in-sync with the repository, and if the repository version has changed from what they are viewing/modeling.
Chris