Integrating this with github a la travis-ci would be great, obviously one would need to be able to make commits to the repository too; I'm not sure if it would be great enough that it would induce people to start paying for the service if they weren't already, though... although I'd sure like it.
I'm not sure what sort of use-cases you are seeing already, but this seems most useful to me personally for last-minute edits to coauthored papers & grant proposals right before submission. Nailing down the final version can be a real pain in the ass.
A few other minor observations:
* uploading a zip file didn't work, but I'm on an old version of RHEL and made the zip with Ark, so... who knows
* after accidentally drag and dropping a bunch of .bbl, .log, .toc (etc) files, I didn't see a way to delete more than one file at a time, or how to undo a file deletion.
* I also couldn't figure out how to move a file from a subdirectory to the top level directory