I have!
But when I quiz them about it, I realise that it's not Shellac that they are talking about at all - it's always another brand and the word 'Shellac' is used by so many salons as a general term for gel polish. This drives me mad, as CND Shellac is a Power Polish and not a gel polish. It doesn't require any buffing of the surface of the nails, or any primer and removes from the nail in less than 10 minutes flat with absolutely no damage to the natural nail.
I have been wearing CND Shellac for two and a half years, with no break at all and my nails have never looked so good.
This is why it's so important, that all CND Shellac service providers sign up for the CND Shellac Certification programme, so your clients will know that you have the CND seal of approval.