Although this was a refurbished unit, I did have some minor problems at first. One of the virtual wall units was missing and the brush retainer broke the first time we removed it (the plastic looked to be bad). To IRobot's credit, they immediately sent a new wall unit and a new retainer, however the replacement was also bad (the plastic was warped and wouldn't fit). The third retainer was fine and again, IRobot responded very quickly. The unit works great, although I don't get the 120 minutes indicated on our carpet (more like an hour 15 or so). For the price I paid for this unit, I can't fault it and although I'm not sure how it will hold up over the long term, it does work well now and I'm impressed with the quick response I've received from the company! The longest hold time was about 10 - 15 minutes.