I have the cheaper "boots and barclay" Target brand version of this. LOVE it!!!
I have two cats that use it and I have to fill the reservoir about once a day, but that's no biggie. About once a week I take it all apart, clean it with dish soap and rinse out the filter, then fill it up and off it goes!
I read that they can get loud if you don't clean them frequently - because gunk will get up in the motor. If you notice something floating in it (like cat food) clean it out right away and you should be just fine. My experience thus far with mine has been GREAT and we've had it since December.
I love it and the kitties seem to as well.