If you are overfiltering, you might get away with it.
The only thing that ever worries me about overstocking, is the stress level of the fish.
I understand what you're saying...I'm not a big fan of the 1in per gallon rule either. But, I think of it this way: I can survive in a two room apartment with 4 roommates, but do I want to? It's just like fish. True, some don't require that much room, and others are completely happy with their tankmate on top of them, i.e. tetras (You can put 15 in a 10 gallon tank, and they'll still breed more). But, I'd rather have room, myself, for those fish that don't like having another fish on top of them.
If you are only keeping one type of fish...then I'd say that 1 gallon rule might not apply. But, when you put more than one species in a tank...I go with that rule, since it keeps fish safe, and less stressed.