This thing is amazing. Our pool is not small -- 20' x 45' -- and it does a remarkable job keeping the surface clean. Not only has it saved me at least 1/2 hour a day netting the surface, it also makes the bottom cleaner because fewer things get a chance to sink down. It has significantly reduced the frequency at which I have to clean the return skimmers. One thing I had not reckoned on was that, since I don't need to use the return skimmers as much to clear the surface, I can run my pump at a significantly lower speed. I haven't quantified it yet, but I'm sure that will reduce my electric bills and increase the longevity of the pump. It's a little workhorse.
So why only 4 stars? The cover latch broke, and I am a little concerned that the latch may be its weak point. Fortunately for me, Sam's took it back and exchanged it for a new one, which has been running without a problem. The app also doesn't do too much, but it does enough. Since the robot runs on its own without any guidance, the only thing I use the app for is to get it to come to me when I need to empty its basket.
The upshot is that I am shocked that I had never heard of these things before this year. The amount of time and effort it has saved me makes me sorry I didn't get one years ago!