I recently bought a set of irons with these installed. I also bought a set of Catalyst shafts to replace the Program 15s if I didn't like them. The Catalyst shafts are going back. I have a smooth swing tempo and they're great for me. They might be good for an agressive tempo swing too, but that's not something I can test.
As far as swingweight goes, I use a JumboMax Ultralight Small Grip which weighs about the same as a standard size grip. My swingweights came out to D2 on most irons. The PW and GW were a little heavier swingweight, but not enough to notice. My 5 and 7 have a SW of D0 so there is probably some variances in the shaft weight distribution. If you use a midsized grip, you'll definitely need to add some tip weights to offset the additional grip weight (usually about 3 SW points).
At $15 a shaft, they are a tremendous value. In the short time I've had them I've hit a lot of approach shots that start out, and stay, on target.
