Tidy Cat used to work great... the pee always stayed on top. Well the last two plastic containers I purchased- seemed to let the litter go right to the bottom of the box. and then,(as we all know) it's hard to scrape off the bottom. and that's with about 6 or 7 inched of litter in the box.
I don't know why companies are always trying to improve something that ALREADY WORKS!