First off, the Keyboard Cover simply feels great. It doesn't add much heft to the phone, and the keys themselves are well separated and offer a decent amount of feedback. It's not as fluid as BlackBerry's keyboards, but I was able to start typing easily with very few errors (and I'm not exactly a master of tiny phone keyboards). The process of attaching and removing the Keyboard Cover was also very simple. Samsung's phones will automatically readjust their displays to make room for the cover (it relies on sensors to be detected, not Bluetooth), and it stows away easily on the back when you don't need it.
I'd have to spend more time with the Keyboard Cover to make a final judgement, but overall it seems like a particularly smart product for Samsung. It addresses an issue with a (small) portion of its users, and it's also surprisingly well implemented. The cover doesn't feel cheap and the typing experience is pretty satisfying. I've gotten used to dealing with software keyboards, but it honestly felt refreshing to have traditional keys under my fingers again.
While it's hard to imagine many people will shell out $80 for an accessory like this, it might be just the thing diehard keyboard fans might want. If anything, it should be appealing to the productivity crowd that the larger Note phones already target.