My daughter recently moved to them from nike pro combo irons, and she loves them, finds them easier to hit than the nikes. the shaft my daughter has is the Nippon NS pro 950. she plays off 4 handicap so i would say are suitable for most handicap range.
Gorgeous looking irons and if I was good enough I would use them in a heartbeat. They are a couple of years old now though and have been replaced by the MP53.
Got MP52's and they are great. Gorgeous looks, great feel and they are forgiving (if only slightly).
I would recommend them, as already said, Mizuno don't do bad irons.