I have one of these that I bought from Woot in September 2012. Here are my impressions:
Overall, I was unimpressed with the sweeping function and primarily used this only for mopping. If you will get value out of having small bundles of hair/dust/etc around the edges of your rooms, then this baby is for you! For a multi-pet household like mine, it was an exercise in futility and a few months later got a Neato which functions much much better.
Mop function is pretty good - does not often get stuck, but as others have said you will likely need to sprinkle some water or cleaning solution around the room since the pad tends to dry out somewhat quickly. For someone who rarely actually mops, this thing is a godsend and it does pick up quite a bit of dirt. My only real complaint is that it's not quite heavy enough to get the job done properly -- the weight of the device doesn't quite exert enough pressure to be as effective as I would like.
I have cats and dogs and as stated, the sweep is fairly useless in my book and I opted for a robotic vac. When the mop encounters small amounts of cat litter, everything is usually fine, but I've found this really depends on how saturated the pad is and how much litter is scattered around. Sometimes damp litter will get pushed around a bit in neat little arcs which is... ok I guess? Overall I'm pleased, but suggest running a vacuum immediately prior to using this.
As mentioned, I've had this for a couple years and haven't had any issues with it, but now I only run it occasionally. To the person asking about getting over dividers, mine was able to climb over small door trim dividers between rooms without much of an issue, but the clearance needs to be pretty low, otherwise it will stop and turn around. When you run this, it seems to simply go back and forth across the whole area, but sometimes I noticed it doing random diagonals to random spots where it would resume. If there's a method to its madness, I could not figure it out.
Thus far the thing has been reliable and I have no major complaints. I will say that since there's no scheduling function and because the device is a bit too light to 'scrub' to any degree, you may be better served buying a steam mop (which is what I did).