Well, I've been in several shops with my Tikit (and prior to that my Giant Halfway)... and never got a negative comment about it. And I'm not just talking supermarkets, I'm talking small shops too.
Heck, I never had an issue even with my Giant Halfway. I would fold it in half, push the seat down and leave the handle bars up. This allowed me to roll the bike by pushing it with the handlebars. I walked into many a shop and restaurant with it, and never had a problem.
That said, I do agree that the Brompton, if fitted with the proper wheels is at least as good as the Tikit (if not better) for this sort of use. But I would caution you that dismissing the Tikit for its folded size doesn't match up at all with my experiences in the "real world".
--sam