The advantage with iRobot is that they have been around for years. Can find the spare parts even in Spore I've taken a look at the local & overseas prices & they are about the same. So if I decide to get an irobot it will be from a local source.
I've actually ordered an Irobot Brava mopping robot. haven't decided on the vacuuming part.
Just took a look at some of the old fashion Dyson vacuum cleaners & the models I was interested in uses lithium ion batteries.
So many of the things that I use now rely on batteries: handphone, iPad, bluetooth speakers, Macbook, portable irrigator, electric toothbrush,....