I've been using nylon bushed servos for years and years in .40-sized and smaller sport planes, and I still use them, and they work just fine. Though with BB servos coming down in price so much, I now have a mix of types. You really have to be pushing things for you to start to notice the difference, and I frequently forget what is where. I do agree that you should match servos on things like duel aileron servos, but I mix and match in planes all the time, like having 4 differnet brands of servos in the same plane. (Had a JR, Hitec, GWS, and Hobico). (only downside is that it makes keeping spare parts straight a royal PITA. Why can't they all use the the same @#$@ spline diameter and tooth pitch?!?)