Personally, I love my 900 Hot Metal irons. With them fitted for me, I can't imagine a better golf club unless I could still swing consistently enough to play a forged iron.
It's funny, but the way I see it, a lot of game improvement Mizuno clubs look like what other lines refer to as their pro club. It's just the look on the back of the club I'm talking about, not the sole, but it seems so many pro line clubs these days have gone to a cavity back look. Not too many still make a muscle back blade, do they?