I have heard issues with it being too try for rats who can end up with feet or tail sores but I don't have personal recommendations soley because it makes me sneeze like crazy...I think that is a personal allergy issue though lol.
I am a fan of the unscented paper pellet litter you can get in the cat section (and sometimes small animal section) of stores like petco or petsmart. Easy to clean up, keeps smell down considerably, and lasts longer than wood shavings or paper crumbles.