James Kendrick has a blog called "Mobile News" on ZDNet.
On April 22, he reviewed a keyboard for the iPad that he called, "the best I’ve tried so far." It is the Logitech Ultrathin Keyboard Cover , which combines the Apple Smart Cover with a full keyboard. It works with the iPad 2 and the New iPad, but not the first iPad, and costs $99.
You can read his full report here: http://www.zdnet.com/blog/mobile-news/hands-on-with-the-logitech-ultrathin-keyboard-cover-video/7567?tag=nl.e539