I didn't quit GMing C&C because I have any problems with C&C. I quit GMing C&C because my players (with one exception) fundamentally don't get the fact that C&C has a different gaming objective than 3E, and the effort to focus on that objective as a GM is wasted if the players aren't going to pick up on it.
3E focuses on the creation of a game piece, the character: all aspects of the PC have numbers associated with them. As bolie says, the personality is represented with numbers and modifiers. However much role playing you tack onto it, the game is a tactical dungeoneering wargame. This trend exists from very earliest D&D - I'm not saying it isn't valid, just that it's not my style or the basic C&C style.
My approach, I guess, is the 2E approach (although 2E rules are, to my mind, inferior to 1e, 3e, and C&C). The interaction with the fantasy world is primary, the wargame secondary (but vital). In this approach, comprehensive rules can be a straitjacket. I had a player tell me in 3E that because he rolled a high diplomacy roll (I forget the exact skill) that he was entitled to have a particular NPC react well to him. That's not the game I'm playing, but it is a reasonable complaint in 3E - after all, he chose that skill at the expense of allocating the points elsewhere. Bolie notes that the rules are inconsistent - to my mind, examples like charging are simply a matter for situational resolution: ask the GM, "can I charge?" The idea that players are entitled to know in advance what exactly they can do (the "playing piece" concept) is appropriate to a wargame, but when it isn't there, that's not a sign of poor game design, it's a sign that the game is literally different from a pure wargame.
My players (again, one exception, to be fair) aren't grasping the fact that C&C is quite different from the wargame-with-roleplaying. It is roleplaying-with-wargaming; this is the reason for a new set of rules - not just to make them lighter. My players are locked into the idea that they are still playing 3E, just with fewer rules. If I can't (and I have given up at this point) get them to understand that C&C is deliberately not 3E, then I'm just banging my head against a wall. I've had a player ask me "since we keep using 3e rules to resolve the ambiguities, why not just play 3e?" That's a total "don't get it."
It's a matter of having a fundamentally different approach to the game than my players do, not because I'm dissatisfied with C&C. For all they complain about the rules, they never learned to play the game.