Summary: I bought this scanner recently. Great feature is the ability to instantly and quickly scan documents double-sided in a single pass. Of course, it's not a flat bed, so only expect to scan individual documents. USB-powered scanning is maybe twice as slow compared to when power is drawn from mains, but it's convenient not to have to plug into mains. Overall - recommended.
Summary: I have owned another ScanSnap prior to this model, the larger S510M and it was very good. So seeing this smaller model, I decided to give it a go and picked one up from BMI Solutions. When it arrived, I was amazed at just how much desk space it saved me, this thing is tiny. It measures in at 284mm X 95mm X 77mm and weighs just over three pounds. The size is only this small when closed. You have to flip open the top flap and extend a paper support when scanning.