I have one. It's amazing except I make too many typos with it. It's programmable from the keyboard itself, like the Kinesis, you can remap keys, switch it to dvorak, etc. But actually, it's the best mousing experience I've ever come across, nothing comes close. You can type and mouse seamlessly, without moving your hands. Sliding 2 fingers of the right hand moves the mouse. Sliding 2 fingers of the left hand, moves the cursor, and at the speed of your hand! And it works even in text terminals, linux, whatever, no drivers or anything needed. I mean, I'm typing this long line in bash, and I can super-fast slide the cursor to the any point in the line this way, even in console mode!
Apple is slowly trickling some of the amazing gestures these boards have to their macbooks and ipads since they bought Fingerworks, but they are still behind.
At these prices you really should have bought one !
