[nbernard]

> The "fig" file format, being text, is easy to drop into source control.

Yes, and using transfig it can be transformed into whatever format you need. So, for instance, you can have a complete LaTeX document with .fig figures (and a Makefile to "compile" everything) in a repository.

By the way, like Ipe mentioned in another comment, it is possible to use TeX formatting in xfig and the .fig format (using the "special" attribute) to produce some especially nice figures for scientific documents.