I have loads and love them - but the cheapo ones from the £shop (or some £1 ones in Homebase) seem to be just as good as the expensive proper E-Cloth ones. I have loads of both and don't really notice much difference (unless when doing glass, for which E-Cloths are much better).
I only recently bothered to try these and think they are worth it- bought a pack of 2 scotch brite microfibre cloths and they seem to give extra friction that cleans marks away quicker. My only problem is that they look grubby quickly, but a soak in bleach would probably help.
i wash mine in the machine alond with tea towels with no softner come up a treat i think n the label it said they are good for 100 washes there fab [blush[ at the fact i hold such a high opinion on cleaning items