If you're in the HN demographic that likes to live in small urban apartments then you may not see value in automated vacuuming, but believe me they are filling a need for many people. My 68 year old mom decided to get one last year, prompted by discussions with several of her friends. She loves it so much that she's become something of a Roomba evangelical - last I checked she's talked 4-5 other people into getting one, and they all love them.
I don't even have a large house (~1200 sq ft), but I do have a cat. The whole ordeal of vacuuming probably took me at least 45 min to an hour every week, and often it didn't get done weekly. Getting a Roomba was amazing for me. It runs on a schedule twice a week, and I only spend a couple minutes dumping its dustbin.