We've always used breeders choice (I think that's what it is - it's green pack). We started using it because the petshop we got our first cat (who is now in cat heaven) used it and she was already used to it.

We are currently changing it twice a week coz we have a new kitten. Before we got the kitten we only had to do it monthly if that because our other cat does his business outside. Can't wait until the Kitten prefers to do his business outside too. I had forgotten how rank it smells!