They’re not a complete replacement to self operated ones, they just keep on top of the worst of it until you can be bothered to do your next thorough clean. I knew this going in from completing a bit of internet research.
That said our Roomba 770 does a great job of the areas it has done, both hard and carpeted. We do have an open plan home, but I find it’s best if we confine it to a smaller area with the virtual walls because it’s designed to randomly cover the area more than once coming from different directions. This means it reportedly takes longer to clean than the other makes, but it does a more thorough job. Therefore it’s set to clean most days and I go around repositioning the virtual walls and/or opening/closing doors when an area is falling behind. I don’t care how long it takes either, we’re not there when it’s cleaning.
Even if it didn’t clean as well as it does, just the fact that it keeps on top of our cat constantly molting everywhere everyday from the moment you finish a clean yourself, that is worth the price alone to me. Note to self, don’t get a fluffy white kitten again.