I commuted 10 miles/one way on a cheapo that I bought from Yan, a contributor to BF and a importer of DowntubeFolders.
It was great! Infinitely adjustable and with a big plastic cat litter tub strapped to the back as a waterproof trunk, very utilitarian.
IT would squirt through traffic like a little water flea. The only issue I had was that it was hard to stand and pedal, but I just
geared down instead of mashing on that bike.
I put Schwalbe Big Apples on mine and the usual mirror and stuff and racked up lots of miles until the cheapo derailleur finally
just wouldnt work any more. I will fix it eventually . . .