We've had a Roomba for a couple of years...
It works fine, we just hit the "Clean" button on the way out the door in a morning and its done and back on its recharging station by the time we get home from work. We use the lighthouse things to keep it out of the kitchen (it got into the cats' food bowls and made a terrible mess the first/only time) but it does the rest of the ground floor (2 rooms plus hall) no problem.
We could use it upstairs (it will detect the edge of the stairs so it cleans up to the edge but doesn't fall down them) but the junk on the floors - especially in the kids' rooms - makes it more hassle than its worth. Bonus: That means the hoover lives upstairs now, so I don't have to lug the thing up and down stairs.
Ours came with a voltage converter (240v-110v). I'm surprised the one on review didn't But then again, we got ours from a UK importer (via ebay).
You must remember to empty the small dust container (and wipe/clean the filters!) every day. I also have to cut the long black hair from around the bristles every few weeks (my wife must be moulting). Our normal hoover has the power to cope with long black hair wrapped around the main drum, but the motor on the Roomba isn't powerful enough.
The Roomba goes under the furniture just fine. It scared the hell out of the cats though, they used to hide under the chairs!