Looking then at how the Roomba performs, its lower height and slimmer width meant it could get in and under things that the Samsung Navibot couldn't. Thanks to its edge tracking feature it also has a more persistent attitude towards obstacles; whereas the Samsung would simple turn round as soon as it bumped into an obstacle, the Roomba has a good old go at getting itself in and around the object. This was particularly effective for chair and table legs, though at one point it did manage to get itself under the legs of a wheeled office chair and failed miserably to get itself back out again.
The edge cleaning also means the Roomba does a much more thorough job than the Samsung, which consistently left a strip of dirt several inches wide around the edge of room. However, this was only true for if you left the Roomba to its own devices in a fairly clutter free single room. More complicated layouts completely flummoxed the simple navigation rules leaving the Roomba completely lost.
To test it we let the Roomba loose in a flat, which consists of an open plan living room (well stocked with dining table, sofa, arm chair, tv, etc) and kitchen, a dogleg hall way, a couple of bedrooms, and a couple of bathrooms. Starting in the living room, it covered about half the living room before heading off down the hallway where it preceded to trundle up and down the same area at least half a dozen times before letting out a rather cute whimpering beep to indicate it had run out of battery (it obviously hadn't been full).
Returning it to its dock to charge then setting it off in a different direction, it did the other half of the living room but then got stuck in a loop going from arm chair to sofa to clothes drying rack (where it would go round in circles for a few minutes as it tried to get out from under the legs) then back again. Quite simply, if you have a remotely complicated house setup then the Roomba will simply not be able to clean the whole lot.
What makes this worse is the docking station requires the Roomba to have line of site – it just uses infra red – to guide it home. So if you set the Roomba going and it gets a bit stuck you're almost guaranteed to still have a dirty house and a dead Roomba cluttering your hallway. In contrast, the Samsung Navibot flawlessly cleaned the entire flat (edges not withstanding) and found its way back to its dock to charge completely unsupervised.
The final death knell for the Roomba 520 is that like the Samsung it doesn't actually do all that great a job of picking up dirt. Sure, it picks up loose stuff from hard floors and short carpets but if you want a proper clean you're still going to need a decent vacuum cleaner. So, despite being only £250, we can think of very few people we'd recommend the Roomba to bar those with the most sparse and simply laid out flats.
One small plus point is iRobot actively encourages people to play around with and program their Roomba's and there's a thriving community of people doing just that. So if you fancy turning your Roomba into something more useful then the option's there.
Despite being the poster child of the robot vacuum cleaning scene, the iRobot Roomba, or at least the i520 version we've looked at here, simply isn't up to the job of cleaning most people's homes. It may be cheaper than the competition, but it also pales in comparison. If you've only got £250 to spend on a vacuum cleaner, just get a manual one!