You are correct. I fly on CO from EWR to LAS often. Most flights are on 757s (sometimes the 757-200, sometimes the 757-300). Even in F, these planes do not have in-seat personal video screens. It is just the movie (followed by a sitcom) on the cabin screen that might be hard to see depending on your location. Still, I generally find flying on a 757 to be much more comfortable than a 737, despite the width being the same.

ClipperCFX