I just use plain-jane AA's. So far, I'm on my second set(I think 2nd, maybe still the 1st), and I've put close to 100 rolls through mine so far. So batteries don't get eaten up THAT fast....
then winder is very convenient, and I've found that when hand-holding the camera, due to the added weight, it helps to steady the camera.
just make sure to slide the little door on the bottom of the body over so the gear engages the one in the body.
frame spacing: when I use the motor winder, it seems more consistent spacing.
also, if you shoot with a prism and 220 film, its almost like shooting a GIANT 35mm with a rotating back, just not as fast
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75% of the time though, my RZ lives on a tripod.
motor winder is accessory #1 I recommend to others though when starting with an RZ kit. to me, its almost essential, ESPECIALLY when you get past fram 15 on a 220(20exp) roll, manually winding that sucker tires your hand out really fast
-Dan