In V21 if you have Untitled buffers open, and have a project/workspace, Slick will let you close/restore the workspace and it will keep those untitled buffers saved in the autosave area.
I just noticed new in V22: Untitled buffers will also be saved in the autosave area when you close slick and restart without a workspace.
Nice.
Bug / lack of feature: If I have an untitled buffer open without a workspace and then try to load a workspace, slick prompts to "SaveChangesBeforeClosing" and in this case requires a filename for the untitled files.