Count me as a single speed aficionado too ;-)
I like being able to crawl up to a junction, see it's clear, & accelerate away without worrying about cable/ gear/ chain slip, or being in the right gear.
I imagine there are loads of bikes around with maladjusted drive trains that people just put up with because they can't get more than 1 or 2 changes to operate smoothly.
Naturally there are times when a higher cruising speed would be nice, but not at the expense of drive train complexity.
I read your Brompton vs Strida post just after buying my Strida 3 & was relieved at your findings, as I'd considered the Brompton, but just couldn't afford the double(quadruple :-)) cost, as we needed 2 bikes.
The strolling is really handy too. I've progressed with my near-vertical strolling stand, but it's too heavy as it's steel, so I'm looking for some suitable aluminium tube for the final design.