We have owned several different models of Roomba over the last 10-15 years years and my S9+ is my favorite one yet! The self-cleaning feature is wonderful, and it takes a long time to fill up the bags, so there's not a huge expense associated with the self-cleaning mode. I've had my S9+ for three months now, running it 3-4 times a week, and I still haven't changed the original bag. My only criticism is that the bristles on the corner brushes tend to fall out. I notified iRobot of that problem and they sent me some additional ones. I hope they remedy this problem soon, as it is the ONLY negative thing I have to say.