I think this model was rushed to market before all the bugs were worked out! It has some major issues compared with the 985 and the i7. My first s9 had to be replaced because none of the buttons on the robot worked. The s9 gets stuck somewhere every time I use it and it's not always in the same place, under tables, under chairs, on carpet, against the rugs and counters, etc. It skips scheduled rooms, cleans rooms that aren't scheduled, misses spots, gets into tight places and then can't figure out how to get back out, it bangs into walls and furniture with a lot of force and it can actually move my chairs and end tables. I will be returning the s9 and going back to the i7. The i7 never got stuck, cleaned effectively and kept to the schedule...the s9 isn't as impressive for the price!