Meir,
My hesitation, after playing with the workspaces and projects plug-in this morning, is the Groups integration. Groups, to me, are a way to get EmEditor to dynamically set up related files and not worry about how the file set was generated or having to save the file set. Combining the groups into the project arena may negatively affect this capability.
Combining the Project and Workspace I don’t have as much problem since I don’t use either one. I do like that workspaces are integrated into the core and appear on the tray icon menu and have their files auto-open when the workspace is open. If other open groups could be (optionally) left open when a workspace is opened then I would be far more likely to use it. Projects are too heavy weight for me, and with all the different menu options appear to be bloat if added to the core, but others may have different opinions/needs.