>An out-of-process server is an exe too, so it can be run just like a regular app. Your app might double as a user app and host to one or more COM servers. So, UI is unlimited, but its utility is questionable.

I don't think so.

Every standalone app I've built recently (ok that isn't too many since most are Web apps <s>) has an external COM interface exposed as an EXE. THIs is extremely handy and basically allows programmatic control to most of the application. Since everything's an object in the app a simple class factory lets you get control of almost everything including business objects in the app with just a few exposed method of the server.

For an idea what I'm talking about take a look at HTML Help Builder - it's a full COM object as an EXE which exposes it's internal project object as well as the UI via COM. There was almost no extra code to write to provide this functionality - it's all there and just exposed via COM.

+++ Rick ---