World's Best was one of many attempts at finding the perfect kitty litter.  I originally liked the thought of a biodegradable litter and I've tried a few but this was the least favorite of the bunch. 

Pros:

1. World's best did clump well and cleaning the litter box was pretty easy compared to some other brands It does crumble a little but nothing unmanagable though. 

2. The granuals are small and my cats loved the liter

3. It did in fact last a very long time

Cons: 

The granuals would get caught all over them, and not just their feet.  It would collect on their fur near their rear...