Our Roomba 520 did a good job for over 4 years now. It still uses the first battery and performs quite well with it.
The only feature I’m missing is time scheduled cleaning. A convenience feature nothing more but nothing less even.
I would not give up the comfort of a Roomba according to my experience with the 520, bought just for testing its potentialities but convinced better than ever expected.
iRobot has a new vacuum cleaning robot, the Roomba 880 with its new cleaning technology ‚AeroForce Extractor‘.
http://www.irobot.de/shop/shop/Roomba/800-reihe/irobot-roomba-880-staubsaugerroboter
This should pick up to 50% more dirt according to iRobot.
The brush rotors are replaced with brushless ones, which shall reduce the maintenance needed to remove things like hair.
Especially pet owners will appreciate this faculty.
Actual price in Germany is about 720 €.
A very detailed test and report can be found on The Verge