As long as you understand how they work and how to set them up, they're great. As mentioned, they aren't deep cleaners, so use your big vacuum to do your whole house before they arrive, then just run them every few days to keep the surface clean. I rarely ever use the big vacuum anymore. They do get stuck on obstacles, so you need to keep the floor clean, and you need to prepare the floor for them. If you have speaker wire or lamp cords, tuck them against a wall or put some wiremold up to hide them. Watch out for places they can get stuck, like if a couch doesn't have much clearance. The first time you run them you'll probably see the problem spots. Also, clean them out at least once a month - dump the bin and use the thread slicer (the blue tool that comes with it) to clean off the removable brushes.
Other than that, I have a small fleet of them working daily as my robotic slav-, er, maids, and they do just fine 🙂