An old riding buddy of mine loves his Brompton. When he got it, he could dis/assemble in 15 seconds or so and htought he could cut off another 4 or 5 with practice.
Bromptons are indeed great commute and bar bikes since you can stash/check them indoors safely. Theft deterrent depends on the fact that nearly nobody knows what the hell they're looking at and/or have no idea how to transform one even if they cut the unlock.
I used to commute on mine exclusively for a year and it was great. It was only when I wanted to have a full rack and panniers that I stopped. I honestly don't know why I bother with full sized bikes when I'm not in roadie/Lycra mode.