I had this box for a couple of years and it was getting kinda yucky.  So I decided to replace it with the newer model (not sure of the number, but it was the more rounded one with metal rake).  I hated that one and after about 3 months went serching for this one again.  The 700 is just the right size.  I like how it rolls up at the end of the cycle before tipping back down to dump the "load".  The plastic rake works just fine.  It is used by one cat, but the bin still fills up pretty fast (about a week).  I have read others mention dumping and reusing the bins (I guess this would be fine, but I don't), so there is a continuing cost for the bins.  Over all my cat (Emma) and I love it.