I rode train #6542 yesterday, which makes the connection at Devon (I did not transfer there, though). Some observations:
There was at least one paper sign posted at GCT by the platform doors indicating the transfer point. The conductor made numerous announcements before and after departing Grand Central regarding the transfer, including the car (fleet) numbers that passengers would have to be in if they were transferring. Around Fairfield, 113 with a mini set passed us at a good clip, headed to Devon for an equipment swap. I'm guessing that once arriving there, the crew did a quick backing move to clear the main, and then changed ends at the platform - maybe someone can verify this? Our train paused at Bridgeport, with the conductor once again making announcements both for passengers onboard as well as on the platform. People seemed to understand, as I did not observe any confusion. When arriving at Devon, conductors exited to the platform, and allowed ample time to make sure all passengers that needed to exited the train. Overall, this setup seems to work well, albeit slowing down the schedule.