I know a lot of people use it for uros, but there are a couple problems with it: It gets moldy pretty easily, absorbs moisture in the air, and sprouts easily too. But it is fairly digestable if it is eated in small amounts.
I think it might be OK to use in a digging box or something, but definitely not as a substrate for the whole cage.
I'm not sure about the comfortable-ness of it though, since I've never exactly tried living in it!