[jitter] Breakin up Engine and GUI

People have mentioned creating a GUI and engine as separate entities, then running one in runtime.
What's the recommended method of connecting the two.  Someone just mentioned OSC as a way to do it, but what about netsend/receive or other techniques?
I guess what I'm looking for is some practical experience before I dive in on this one, since it seems like there are a variety of ways to achieve the same results.
I'm a little skeptical, because of all the issues in XP with freeze-ups when you select different windows.  I'm curious to see if I can be outputting from one window and still poke around on another without it causing trouble.  This is one reason any "drag and drop" features of max 5 will be pretty much useless in performance from my perspective.  A integrated file browser would be more useful, if it didn't break the flow of the scheduler. Apologies for digressing.
My current plan is to create an engine with Quicktime players, routing and mixing of signals to textures, GL objects and Rendering.  Then have a seperate GUI for all the control.