Great for the lazy, not so good for the landfill
I have 6 cats( though one always 'goes' outside) and use these when I'm feeling lazy and they're really good. I also buy a 5l bag of catsan and top up the pack to create a little more depth. this way each pack lasts about 4/5 days. the fleece in the bottom is great at soaking up urine, and so easy to change. When they first saw it they had to do a bit of investigation - clawing and scraping the plastic. I find it's better doing this: cut up the stickers that hold the roll in place and use them to secure the plastic liner onto the tray, that way it will survive the scraping better.
the only thing I don't like about it is it's obviously not very eco friendly with all that plastic, so now summer's here (?!) I've reverted to a big sack of plain cat san.