My experience with games that use hit locations and such has been mixed.
In general, when past players have asked me as their GM to attack a specific location (like the head for instance), what they really want is an instant kill.
I can use a system like that... but I always make it clear that if they want a hit location chart that I will use it at all times. That means that the PCs will also occasionally get hit in the head, and that NPCs will also occasionally take called shots.
Once this is pointed out, I've found that the enthusiasm for such rules is reduced significantly. They want to get the occasional one shot kill in, but they're not so happy about the fact that it goes both ways.
Amazingly, I've found that Sunder in d20 falls into the same category. The PCs may or may not sunder enemy weapons, but watch the outcry if you ever sunder a player's current prize weapon.
To deal with that, I kind of keep score. If a PC successfully uses Sunder on anything other than a mook, I set aside a sunder attempt for down the road against them. It seems to work, because I only count their successes... and they use it sparingly.
Now, in Hero/Campions, I'm actually much more enamored of hit locations, because it completely changes the mechanic for killing attacks... significantly reducing the KA Stun Lottery effect that makes KA attacks so popular.