I have a CarryMe. The small wheels are generally not a problem. But it has been a problem sometimes with gutters that intersect the whole street, cobbled roads and dirt tracks. That said, it's not much different that a road bike. I buckled the back wheel already somehow. When I'm in a city I find it extremely useful and it goes on a plane. The main thing is that I know if I get lost or late I can always take a taxi back, which is very handy.
The quality isn't great but it's very useful... I don't feel the need for a Brompton only because I've never used a Brompton...