Ron,
I like the redundency and RF interference protection a isolator/power buss provides. My 6v pack will be plugged into isolator and powering servos only. 4.8v pack powers reciever only. The isolation circuitry provides protection from servo noise, loads etc. especially useing metal gear servos. I have even mounted throttle servo directly on firewall with gas engine and electronic ingnition module, with absolutely no radio interference resulting. Oh, and a metal pushrod too.
For those interested, after talking to MGA via e-mail, I have chosen not to use the 425 servos. Instead have purchased hitec 645MG and 535 Karbonite gear servos. 645's on rudder and ailerons and 535 on elevator's. one on each elevator half, which may mean the additon of a matchbox. not sure yet.
Craig