I have used the ScoopFree self-cleaning litter box for a while now.  I have two indoor cats that only use the litter box.  One week is about the maximum I can get between tray change-outs.  But cleaning is easy and only takes a couple minutes each week.  Very reliable and no fuss between tray change-outs, though the trays are a bit more costly than conventional cat litter. [This review was collected as part of a promotion.]