Not only heard of them, but have them fitted 
Well not quite those ones
http://www.absolutelyshocks.com/ have worked out valving specific to the mx5 and are selling them through http://www.mx5mad.com/ and http://mx5parts.co.uk/
They're nice, so much nicer than my old stock R-spec bilstens etc...
I've not played with them much and keep meaning to do more suspension wise, ARBs Poly bushes etc...
But so far, beyond a minor squeak I now have from the rear right side I have no complaints.
Well not quite those ones
http://www.absolutelyshocks.com/ have worked out valving specific to the mx5 and are selling them through http://www.mx5mad.com/ and http://mx5parts.co.uk/
They're nice, so much nicer than my old stock R-spec bilstens etc...
I've not played with them much and keep meaning to do more suspension wise, ARBs Poly bushes etc...
But so far, beyond a minor squeak I now have from the rear right side I have no complaints.