Just to sound off, I use care fresh. Even with quite a few rats in the cage it lasts pretty well and mostly keeps the odors down. Just stay away from woods, especially aromotics like cedar. Those are really bad for them. I've read the ash or pine are non-aromatic and thus safe, but I have one rat in particular that seems to have a sensative upper-resperatory system and didn't handle pine very well when she was younger, so I've been using carefresh since she was a baby. Personally, stuff like carefresh or yesterdays news are some of the best as far as I've been able to discern. I'm not really sure what the megasorb is so I can't really comment, though if I didn't think I'd have to wash it every other day I wouldn't mind just using something like carpet or fabric. Even cleaning it doesn't bug me, except Punk gets a little territorial about the cage sometimes and nips at me if my had is there too long (only inside the cage).