robot vacuum cleaners

I really like the idea of getting a robot vacuum cleaner to clean my apartment for me.  I mean it sounds pretty sweet just having this thing clean my floors while i'm not there, and I don't even have to lift a finger, sounds like my kind of appliance.  

So I was looking around online because I know very little about these robot vacuum cleaners.  I had only heard of the roomba before.  I don't know anyone that has one, so i can't go look at it or ask them how well it works.  So I asked the internet.

I found plenty of information on them, but mostly what I found pointed to the ones that were good were pretty expensive (~$500 ish).  There were several types as cheap as ~$100 ish but I'm not too sure they are entirely useful.  

I also found this: http://housewares.about.com/od/roboticvacuums/qt/robotskins.htm

which I find fairly entertaining.