I voted "no" because I think that the ability to play two-way offensive shots in 9-ball is a useful and legitimate part of the game, and I wouldn't want to see a rule implemented that would destroy that. I don't think there's anything wrong with playing a bank off the short rail while at the same time rolling at a ball that's hanging in a nearby corner pocket, and I think that a player should get to continue shooting if he/she pockets either one of those balls. I personally don't consider that slop, and very seldom do I see cases where a player is blatantly blasting at groups of balls, hoping to slop something in, even at the lowest skill levels.
I also believe that most of the luck that occurs in a game of nine-ball is due to players missing shots and getting lucky leaves as opposed to slopping in balls, and there's no "call shot" rule that's going to prevent lucky leaves. Especially at the professional level, I think you would find find that there are many more cases of someone missing and getting a lucky leave than someone slopping in a ball. Those numbers would undoubtedly be different at the amateur level, but I would still guess that unplanned safeties occur far more often than slopped balls.
Also, at the professional level I would assume that many of the times when a player "slops" a ball are actually cases where a player was hooked, kicked at the ball and accidentally made it. If you're going to punish a player in a situation like that, then I think you need to be really careful as to how you go about it. I personally feel that it's safer and fairer to reward the player who kicked the ball in than it is to reward the player sitting in the chair.
All that being said, I do feel that calling the 9-ball is a good rule, and I would also support changing the rules to make a 9 on the snap not count as a win, as the 9-ball rack is so vulnerable to gaps and manipulation. Calling every ball, though, I'm afraid is one of those rules that looks good on the surface, but in reality could take something valuable away from the game, especially if implemented without proper forethought with regard to the implications.
As always, JMHO
Aaron