We took 93 North for about a half an hour, stopped at a Dunkin' Donuts, and then took 93 South back -- with some extra practicing on and off exit ramps on the way back.
FCS-Ian thinks I'm doing fine. I continue to feel a little bit nervous -- I think largely I just still haven't internalized all of how it works ... being aware of and responding appropriately to all the stuff around you (traffic [incl. reading what the other driver is thinking and intuiting what they think you're thinking as you all do this non-verbal dance of not crashing and ideally keeping a smooth flow of traffic ... !], exits [I keep feeling like exit ramps pop up suddenly way after I've seen the initial sign and have been looking for warning about when I should start slowing down in anticipation of said exit], etc.).
One of the biggest adjustments, actually, is that I've gotten trained to not manually turn off my turn signal since it does it on its own -- except that when you're just shifting lanes rather than doing ~90-degree turns, it doesn't.