Roombas have become nearly synonymous with the concept of robot vacuums, and for good reason: They're perhaps not the absolute best robot vacuums on the market, but they do the simple things right, and the iRobot vacuums have some of the best user-friendly in-app experiences around. Roombas also tend to get discounted pretty frequently, like the Roomba Combo j5, which is currently $299(originally $599.99) after a sizable 50% discount.
The Roomba Combo j5 can both vacuum and mop, although calling what it does "mopping" is a bit of a stretch for me. The mopping feature is available when you attach a separate "Roomba Combo bin," which you must fill up with water. The attachment drips water into a cloth on the bottom that is dragged on spaces right after they are vacuumed by the machine. It doesn’t provide much pressure, so it won't get rid of any stains. It's more of a light swipe with a damp towel.
The Roomba Combo j5 is good at avoiding obstacles that are on the floor, like cords or dog poop. The only thing that I've seen my Roomba Combo j5 get stuck on are the strings dangling from my window blinds, which sometimes pool on the ground. The battery lasts three hours and charges itself if it needs to more juice to finish a task.
If you don't like the idea of emptying out the debris on the Roomba Combo j5, you can opt for the Roomba Combo j5+ for $150 more. The Combo j5+ is $449 (originally $799) after a 44% discount. The vacuum itself is the same, but it comes with a home base that auto-empties the debris, with the capacity to hold up to 60 days' worth of junk. If that seems worth it to you, consider getting the home base. If not, $299 for the basic Roomba Combo j5 is a great deal, matching its all-time lowest price.