Editing and scrolling a level becomes very slow, even in small levels. To be fair, though, the entity layer is good enough for placing enemies and traps. Changes to the project definition require levels to be closed and reloaded. It is possible to attach custom data to levels and sprites.
OGMO writes project and level data in XML format that is easy to read and write. One thing to watch out for is that the file format uses localised floating point format, so an international team with mixed locales may run into problems when exchanging levels. The rotation origin seems to be the unscaled origin, and scale is the top left corner.
There doesn’t seem to be any written documentation and at the moment the website only contains a few tutorial videos, so a lot of the user interface needs to be explored by trial and error.