Thanks, everyone, for your thoughts so far.
I am happy to have two bikes. It is nice to have a guest/back-up bike. If I added the Carryme, that would bring the grand total to three, although the small footprint hopefully means I could fit it into my bike closet along with the other two.
The Carry Me looks more like a "real bike" to me than the A-Bike. Also, the reviews here seem to affirm it has a much better ride. Maybe makeinu would be willing to let me test out his? (The A-Bike/A-Train combo is clever, though.)
I don't need a Birdy or Swift for the long commute--my Downtube Mini does the job just beautifully--but I appreciate the suggestion.
I've tried a Brompton and love the fold but it is ridiculously expensive and I didn't like the feel of riding it.
I may simply be making things too complicated trying to get everywhere by bike. Perhaps I will simply have to wait for that enlighted day when NYC has a bike share program (like the Paris Velib) to do small jaunts or a chain of bike garages (like the McDonald's Cycle Center in Chicago) where I could park the bike securely.