This is a brilliant product and works really well. I've used it several times now and have been really pleased with the results; I've even had compliments from complete strangers!
OPI have just brought out their own version, but it's much more expensive, and owning both OPI and Barry M nail varnish, I would say that the Barry M nail varnishes actually last longer, and therefore much better value for money!
One tip I would say is, put a clear top coat on, it makes the effect fit in with the base colour much better and looks nicer! (The effect nail varnish has a matt look.)
I hope Barry M will bring out more colours soon!