It works OK on carpet if you don't have pets. You do have to clean the sensors and brush regularly. It's more work than vacuuming. But it's pretty cool to see it work.
I've seen the clones at trade fairs. I think that they'd have about the same chances as spontaneously combusting and burning the building down, than cleaning the floor
The new series (500-something) comes out in HK in 2 weeks. Now, if I could only find a place that sells them. Otherwise, it's Ebay.
I had the Roomba Red a few years ago in Canada. The new one looks a bit sturdier. iRobot has an office in Kowloon, I don't think it's a retail store, but you may want to check with them to see where to buy one.