I don't know if I can give a short, simple answer. The Soldier of Fortune matches were run by Michael Horne and Mike Wadalich for quite a few years. I shot the SOF matches for around 10 years and always thought there was room for improvement. I felt there should be a class for "Open" guns like in IPSC but the guys with SOF were firm on their match convictions, "My match, my rules." They didn't even allow brightly colored magazine bases for pistol mags. They tried to make the match like a real gunfight. My philosophy has always been that until the target start shooting back, this is simply a game.
In 1994 I met a guy in CA who started the International Multi-gun Association (IMA) but he had to stop when he was almost killed in a motorcycle accident in '95. I took it over and went to the Practical Pistol Division at Rio Salado Sportsman's Club in '95 with the idea that we could host a world class 3 gun match like SOF but vastly improved. I got the blessing of the club, and the SUPERSTITION MOUNTAIN MYSTERY 3 GUN was born. We held our first match in 1996 for 67 enthusiastic competitors and a handful of very generous sponsors, with Dillon Precision as the overall match sponsor. From 1996 to 2005 the match and the rulebook grew. Rules are there to try and "level the playing field" so all competitors have an even chance. These matches should be about shooting skill and not who has the latest and greatest accessory that ensures they win. It should be about ability and not "cubic bucks."
I worked on the IMA rules for ten years trying to make sure the game we play is fun and fair. I always believed that the surest way to failure is to try to please everybody. On certain rules and decisions some people agreed with me and some didn't. Oh well, that's life. For the match in 2010, there will be a few new changes. I hope they please most of you. In Heavy Metal class, the minimum caliber is .44. Polymer framed guns are allowed BUT there is a 10 round magazine limit. Yes, that means the 10 round mags are allowed for the single stack 45s also. This match should be FUN.
I have always felt that shooters come to a match for the camaraderie and the excitement of enjoying a shooting sport. If you happen to walk away from the prize table with something really neat, that's a bonus.