Just got one for my in-laws a week or so ago. Not sure if they've used it or not. Basically unless you really need it (health problems so you can't vacuum, etc) don't waste the money. It doesn't do anywhere near as good of a job as an actual vacuum cleaner because it's just not that powerful. It's good for in-between cleanings but not as a replacement.
Buy one from a local store (not online) and just try it and return it if you don't like it.
The Plain roomba is available lots of places, the Pro and Pro Elite are harder to find. The Pro Elite is a Sharper Image, Brookstone, and oen other store exclusive...