The 500 series (I got a 535) supposedly have twice the suction power of the previous models. I can't comment on the relative performance because I've never seen the older models in action, but the 535 seems to do a pretty good job. I'd say it's just as strong as your average vacuum cleaner, but not as good as your high-end Hoovers and Dysons and such, but of course, you don't have to push it around all day to get the job done. As for navigation and floor coverage and such, as long as you don't leave obstacles and stuff lying around in your floor such as clothes and other such things, it will cover the whole floor within reason (obviously it can't get under gaps smaller than it or in between pieces of furniture too close to the wall or other things). It's also important to define rooms for it well by closing off other rooms and cleaning them individually or using the virtual wall and lighthouse addons. If you just let it roam free in your house with every door to every room open, it's not going to clean every square inch of every room. It's not quite that smart.