Pretty useful. Although it would be better if you could just send the diff over the wire when trying to look a previous version -- it takes way too much time to download the whole model.
Being able to continue inspecting the model in the same position it was before loading another version would be nice as well.
I'm not talking directly about your method versus the git method. What I was alluding to: if you're planning to use git to distribute your models eventually, perhaps you should have an eye toward optimizing the models and their diffs for use with git. Then, git transmits only the diffs as needed, when needed.
Being able to continue inspecting the model in the same position it was before loading another version would be nice as well.