Visualize this: Right now, I'm typing this article on my MacBook Air, but my fingers are physically hitting the comfortable keyboard connected to my Windows desktop machine. When I scroll my cursor to the edge of my MacBook screen, it appears on my Windows desktop, and I can copy files and text too — when I took a picture of the cable for this post, I used my MacBook's SD card slot to import the file, I literally dragged and dropped it onto my gaming desktop to edit, and then I deposited the final result right back on my Mac again.
What does this thing do? Simply put, you plug it into two computers, and it shares the keyboard, mouse, and clipboard between them. You can move between both seamlessly, and drag files from one to another (albeit at a measly 20-30MB/s- this thing needs USB 3.0 badly).
Yeah, you can run Synergy, or a VM, or use an old USB switch, but this is a new level of simplicity, economy, and style. Any IT professional should have this in his (or her) bag, and anyone who uses a Mac and PC together should grab one.