There are definitely some features to the new one that make me want one. The primary one just may be that it's supposedly sealed much better, so you don't end up cleaning every crevice of the robot. I've been using my Roomba in my office for the last several months, and it gets pretty dusty in here. When I go to empty out the waste bin, I end up at the sink for half an hour, cleaning the dust out of everywhere.
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Matt