iRobot's Braava 380t
It's great that the Roomba can vacuum your floors. Less great, though, is the meandering, noisy, furniture-ramming way it does so, drunkenly ping-ponging through rooms with none of the stoic efficiency expected from a proper mechanical servant. Which is why iRobot's Braava 380t is precisely the cleaning droid we've been looking for. It's a faster worker, using an infrared spotlight to triangulate its position while cleaning in orderly grids. And since it's not a vacuum, but rather a sweeper and mopper (it uses dry or wet Swiffer-style microfiber cloths), the robot is practically silent during operation. Its discretion even extends to its unassuming, boxy design – you can store it upright against a wall, or tuck it away on a shelf.
Unlike the Roomba, this bot is intended to work almost exclusively on hardwood floors (or similar surfaces). It also requires a modicum of handholding, to swap out used cloths for fresh ones, and to plug it in for recharging. These are relatively minor issues, though. Pad replacement is easy, and no harder or grosser than emptying a vacuum. And in the 12 years since the Roomba debuted, homes have become more hard-wooded places, better suited to the Braava's less-haphazard attentions. [$300; store.irobot.com]