I used to love OKO, until they changed it about 5 years ago and the clumps started breaking up. I guess it depends what type of diggers the cats are. I tried a similar one, called Greenwoods, but it was the same as (the newer) OKO, so I switched to clay clumping - I only do a full change around once a month - even less, since the new cats tend to go outside most of the time. Of all the litters I have tried, Sanicat professional clumping gold seems to be the best. Tesco sell 5L bags for around £5, but I pay £14 for 3 x 6L (the boxes from ooplus are bigger than the ones from Tesco) and that lasts for months. Even when we had Kylie, with her gut issues, 3 boxes last a couple of months.
As with the wood litter, I always found that the trick was to fill it deep enough so clumps didn't reach the bottom of the tray. The clumps set like cement in minutes, so easy to get rid of solids. Important have the right kind of scoop for clay litter though.
http://www.zooplus.co.uk/shop/cats/cat_litter/accessories/98036The bonus is, it isn't overly 'baby powder' scented -just a nice smell.