Ok, I am *starting* to become more clear on them, see if I got it right:

By your explaination, for ActiveX Dll's I will most likely be using Private for my internal objects, and MultiUse for my objects that the user is going to instantiate in their code, is this right?

By the same token, for ActiveX EXE's, I will be using SingleUse mostly because more than one program will be accessing them at one time, and it would be quicker for each client to have their own instance, although more server resources are going to be used?
Are these right?

More questions came to mind on this subject though. Where does the threading model and thread pools come into play? Which setting is most scaleable in terms of ActiveX EXE's?

Thanks for your help.