Sal Zaino was nice enough to e-mail me this reply when I asked him this same question before:
Unfortunately, the jury is still out on them..... Some of them I tested
are excellent and do not scratch... however some are terrible and
definetely scratch.. The quality control of these products from overseas
especially Korea is not consistent.. So you never know if they will be
the same scratch free quality...

Even when using the same brands, I
found the quality to be inconsistent.

It's a shame because I think the
concept is excellent...
For now I do not use them.... I'm still lab testing... Stay tuned..
NOTE: If you are already using microfiber towels.
Look carefully at your paint finish under flourescent light when you are using your towels. If
you are not getting any swirls or fine scratches, from the microfiber towels then you are okay
and can continue to use them... Remember it's better to be safe than swirly.