All modern jet aircraft have computer-controlled flight surfaces, in fact some would be darn near unflyable without them. So I don't see why jet models shouldn't use a full complement of avionics. In terms of other models, I'm curious why people would feel that gyro is acceptable on the rudder but not on other controls. To me the only argument would be that our models are somehow more sensitive on the rudder than the full-scale aircraft were. And anyway, if you're going to ban gyros, you might as well ban mixing as well.