I bought the 4-PW set about a month ago and have played these clubs at least eight times since then, so I feel I can review them objectively now with some playing time on them. I am a duffer, shooting in the mid-90's.
The first thing I noticed is a substantial increase in distance. With these clubs I am consistently 25-30 yards farther than I was with the same older iron. Also: the ball flight is quite a bit higher than my previous clubs. I don't know if I am getting more backspin, but the higher flight is helping me stick longer irons on the greens where before I often rolled off the back.
I couldn't find a Callaway 3 Iron that matched this set, so I made a clone for the three. It hits well, but does not have as good of a feel as the branded clubs. I used to be a big advocate of clone clubs until I tried the clone of this Callaway club and found the clone quite inferior.
I am extremely satisfied with these clubs. I believe it will take a substantial improvement in another club to make me want to upgrade these any time in the future.