my cats are messy and kick litter everywhere but they dont walk it about - its really really good stuff - it doesnt smell, it doesnt even clump like other litters - it sort of fluffs up into a ball that you can just scoop out, it not cheap but i dont ever change the litter tray now - nothing gets wasted because you can just top it up.
occasionally when it gets really low i might chuck the last bit and bleach the tray - but its really cost effective.