Still have my M3L. My take:
Good: Super compact fold, solid incremental engineering, head block for attaching racks that don't interfere with steering, easiest for multimodal commuting as far as taking up the least room, can roll in semi-folded position and use as a shopping cart with the front bag attached.
Bad: Expensive, very limited gearing range, riding position can be wonky for some riders (me included), difficult to remove the rear wheel for flat repairs or tire replacement.
Before you plunk your money down on a Brommie or two, by all means test ride one if you get the chance.