I think basically if you struggle with distance and are a high ball hitter/high spin player due to adding loft through impact they can be a great club for you. If you're a very high swing speed player who puts way too much spin on the ball a club like this IF FIT PROPERLY can work well... you'll just be hitting less club into greens but you'll have to be careful with certain lies. I will say that there are WAY more amateurs that have too little spin rather than too much contrary to all of the ballooning talk you see on here... (keep in mine how high pros hit it). The person these are not good for is someone like me. I'm on the cusp of the "right" amount of spin and height with a players iron. My usual 7i carry is 155-165 depending on loft with around 5500-6500 rpm backspin. If I go to an iron like this my spin drops into the 4000k range and I start to hit a 7 around 180+ yards without enough stop. Put me in a flier lie on the course and I'm in trouble. Keep in mind the course is ALWAYS taking spin away from you - rarely, if ever, giving any back. If you're on the cusp of being okay on a monitor it's not going to be a good result on course.
I use a 10.5 degree driver and would describe myself as a mid to low ball hitter with average spin and my 7 iron was a 165 club. I simply moved to a high launch mid to high spin shaft with these heads and now carry my 7 iron around 175 on a nice high trajectory with zero ballooning and consistent distance control. Finding the best head / shaft combo is key to any fitting, as is a proper ball fitting.