I emailed Futaba about the use of batteries other than NiCDs. Here is the answer I got:

"Those servos are to be used with NiCds only. This is due to the discharge rates of the different types of batteries."

Is this just a liability issue? I ask because I've seen other posts here that say you can use other batteries.

I have some AA NiMHs that are 1800mAh. I was going to use 5 to power the Rx on my Kyosho USA-1 Nitro Crusher. I have a Venom failsafe on the 3003 servo for the throttle, and of course, the 3305 for steering.

Why won't alkalines work? What is their capacity?

I was using a 9202 for steering before and also using regular alkalines and never had a problem. Maybe I wasn't pushing the truck hard enough to see the difference between alkalines, NiCDs, and NiMHs. Hmmmmm..