I'll second the Roomba. I've got several "highly-rated" models that were recommended by Wirecutter a few years ago, and I scooped them up on a sale. These things are pretty terrible. They regularly get stuck on common household obstacles such as the carpet, the rug, and even the wall. More often than not, our main floor Roomba's charging station is empty because the Roomba itself got stuck somewhere and died, or it just decided not to return to its base and powered off under the dining room table. We also have a recurring problem where the Roombas will sit on their charging stations but won't charge, depleting their batteries until we notice several days later and slightly adjust the contact points to get them charging again.

Terrible purchase, stay away from Roomba.