I am a big fan of Mizuno's forged irons, personally, and I've been using their forged irons for the last 15 years of playing this game. I've played with cast iron as well, but the feel you get from a well struck shot on the face of a forged iron is like no other. I can best explain it as hitting a heavy marsh mellow..it's a nice, soft, but firm "thud" feeling that you desire to replicate over and over again. Once you feel it, there's no turning back..be warned:
and why my irons "sing":
I think the 1st iron is a Ping, the 2nd a Callaway and the Mizuno MX-200 (mine).