Last week, I got the “Logitech Ultrathin Keyboard Cover for iPad 2 and New iPad.” (About $100 at Amazon)
I have found it to be totally awesome.
It turns the iPad from a robust content/media consumption device to a fully operational laptop. I haven’t given up the Macbook Pro yet, but this is potentially a low cost replacement. The keys are smaller than the full laptop, but not terribly so.
It uses the magnet feature on the new iPad (3) and works well. It is lightweight, the Bluetooth works seamlessly, it holds a charge for a while, and recharges quickly.
My only complaint is that when I type, my middle fingers occasionally touch the screen, which makes the cursor jump. Touch typists and people with normal length middle digits should not have this issue.