I've used CocoBlox... great stuff. The last batch I also bought in bulk... I only have 4 snakes, but just store the stuff in the shed, no biggie.
With that said, I find it to be pretty much the same as ReptiChip, so I always go with which I can find for cheapest.
Nikkibus, how do you compare CocoBlox with ReptiChip? You use more of it, so maybe you notice a difference. For me they seem the same.