I suspect I know the answer to this, but...
In 10.7, versions of a document are saved automatically. You can also explicitly save a version by selecting "Save a Version".
When I wish to revert to a previous version, in the Time Machine-like display that appears, there seems to be no way to identify which versions it's showing me were saved automatically by the system, and which were (what I consider to be) the "milestone" versions that I saved explicitly.
Am I missing something? I know you're given the opportunity to revert to the last-saved version when you select File->Revert, but what if I just want to look at that version first, or revert to the last-but-one saved version?