I think most yards would still have areas or borders that would require a conventional mower or, at least, some intervention.
I have over an acre (5000 sq m) to mow. Here in NC, that's once a week from mid-April to mid-October. Having it mowed by a service would currently cost $1200/year. I've been prepping the yard for eventual robotic mowing since Hurricane Isabel wiped out most of the wooded areas in 2003. The setup now can be done entirely from a riding mower without any trim mowing or edging. Takes about 1.5 hours.
With the possible exception of the size of my yard, I'm the perfect prospect. I was one click away from buying one of the above a few years back, but Debbie said I'd end up having to do more in support issues than it was worth. Basically, I'm waiting for the technology to prove itself and also get cheaper. In some ways, it's encouraging that iRobot has taken so damn long to bring theirs to market but I'm going to have to see a lot of rave reviews before I buy. And the price needs to be under $3k.
