Like Synergy[0] with file copy support (dragging across screens), but non-free and Windows only? I advise everyone to try synergy, it's a great experience to have the mouse leave one screen and enter another (even if it sounds kind of trivial).

[0] http://synergy-foss.org/

Nice, they took Synergy's idea and made it proprietary, without even a mention of where they got it from. The article nor the Microsoft website mention that Synergy has been doing this for over 10 years.