I bought a Roomba i6+ on Amazon and it just finished its first "vacuum everywhere" command. The i6+ is essentially the same as the i7+ but is unique to Amazon. I think the differences are that it's gray instead of black on top, and it doesn't come with spare parts, bags, filters or brushes. The "plus" in the name refers to the charging base that includes a vacuum that sucks the dirt out of the robot into a disposable bag. It was $550 on sale instead of $800 for the i7+ at Best Buy. Blow that dough!
Anyway, I was pretty impressed. It automagically maps up to 10 floor plans so that should work just fine as I only have two floors. The first day after I did the initial mapping run when it worked hard exploring the house and raising clouds of dust I customized the map by adjusting the room dividers it had guessed at (which were sorta OK) and named each room. I also figured out that while it can eventually manage to get around dining chairs it did a lot of bumping and twirling so next time I put the chairs up on the table restaurant-style.
It vacuums each room in a rational pattern, "mowing the lawn," and the pattern is supposed to get better as it learns the house. It worked on one room at a time and as it finished each room it ran around the walls of that room for its final pass. It even did the same thing around the edges of furniture within the room.
The main floor of our house is around 1700 sf (the robot reported exactly how much it cleaned but for the life of me I can't find it again in the app). It took 5 hours and 12 minutes total, including stopping for two recharging sessions of about 1.5 hours each, and going back to empty itself at least 3 or 4 times in addition to that. It's fun to watch it march back home, futz around trying to find exactly where the charging station is, and dock itself. I'm glad I don't have to bend over and manually dump it so often.
Anyway, so far I'm glad I bought it. While not overly loud, the constant whirring got a bit tiresome so I think from now on I'll tell it to do a handful of rooms in any one day. Tomorrow I'll take it downstairs and have it map those rooms. Supposedly, all I have to do is set it down anywhere in the room and hit the "go" button and it will recognize it's in a new space and map it in a separate floor plan.