I have the same exact feeder as rstampa on page 1 of this thread, am using crumbles. They seem to go through them a little faster than pellets. I could be wrong, but I think the crumbles are pehaps a little easier for them to digest, vs. the hard pellets that I've also used. My only reason for saying this is that one of my chickens consistently has a bigger crop than usual at the end of the day, she's always been this way and doesn't appear to have any crop problems per say.. but anyways, this issue seems much less of a deal when she's eating the crumbles. Same deal when I feed her scratch grains for a snack, crop get's huge. I think the density of the feed plays a role in that whole thing. I rotate in a bag of the pellets once in a while just to keep them from getting to picky about one or the other.
Mark