Good things: It's a great design and it's easy to pick up since it's a lot like wrapping the top and bottom qwerty lines up around your fingers - the same fingers for many of the same keys, but no chance of misreaching and mashing two keys. The keys are magnetically held, and you push them out through an optical sensor - so there is a definite feel of breaking the magnetic grip, but you aren't whacking your fingers into a solid stop like a normal keyboard.
Bad things: The one I have is old and emulates a serial mouse, and Microsoft took serial mouse support out of Vista. The mouse emulation is serviceable but not brilliant. It's slightly awkward to extract your hand to reach for a mouse without pressing keys. You can't type one handed and hold a mouse/phone/mug of tea. No numeric keypad.
At work, the need for a mouse and phone made it awkward, at home I don't type enough solid blocks of text on a desktop computer (it's not much good for laptop use either).
I still like it and like the idea, but it's in a box, unused, because it's mildly inconvenient.