The iKeyboard just arrived. Before reading further, just click on the hyperlink in the last sentence and take a quick look at it.
The keyboard sticks on over the iPad's virtual keyboard. It has raised squishy plastic keys that give you tactile feedback. You won't be able to type as fast as on an Apple Bluetooth keyboard paired to your iPad, but quite a bit faster than on the virtual keyboard. One advantage over the virtual keyboard is that you can rest your fingers on the keyboard, so touch typing is actually possible. Another advantage is that it needs no pairing or batteries. I find pairing the Bluetooth keyboard can sometimes be tricky and time consuming. The iKeyboard is ready to go.
I would say that if you are planning to take a semester's worth of notes, get the Bluetooth keyboard, and maybe the Origami case. But if you want a keyboard you can tuck into the Apple Smart Cover (the cover will still close) and practically forget about, this is your weapon of choice.