We have three sheets of it, it's probably about 10 feet wide in total, usually more than enough to get a few people together in shot. We don't have any of that floor covering stuff, so if we need feet to be in shot, it's roto only.
The screen does get a bit dirty through continual use and dragging out of storage, but it's held up well so far and still gives pretty good results. The main issue I've noticed with it is that the light from the LEDs doesn't easily get through small gaps. So the space between people's legs or under their arms can often come out grey because the green light isn't hitting the area behind them properly.
Heh, if we were making some professional thing, I'd probably consider alternatives, but it's served our purposes well enough.
EDIT: Chromakey demo from our first film. This was all shot and keyed in SD back then, so excuse the quality of the comps! We've got a little better since.: