We have one in our Fleet, and the negatives I've seen are that it is very difficult to get response and parts from the factory. Our guy lost his mast (accidently released the main while under spinnaker in a puff), and it took a LONG time to get the replacement. He's also noticed some flexing and gel coat cracks on the decks.

The fellow I bought my NACRA 6.0 from had sailed and was a dealer (I think) for the Mystere. He said in a straight line it was faster than the NACRA, but if there was any tacking or jibing involved the NACRA would come out on top - the basic difference being that the NACRA 6.0 has more rocker in the hull than the Mystere.