We have two now.. one for downstairs and one for up stairs both are great. You do have to stay on top of maintenance I.e. cleaning out waste bin and sensors on a regular basis. Also you have to ensure the floor areas are free of any object that can hinder the progress.
We have 2 Neato connected, they are good we chose them because they had good reviews of tackling carpets which we have a thick pile rug downstairs. It manages this very well and always a delight to come home to see the place has been tidied. As for noise they are a little quieter than a normal hoover but not quiet enough to run at night... there is a eco mode which is meant to be quieter but I want it to clean not mildly suck.