I could go on, and on about how fantastic Mark Pilgrim's technical writing is, but if you cared you would already know. He's working on a HTML5 book, and the chapter about forms was posted today. Here's a quote about the new "email" type for form inputs:

To sum up: there’s no downside to converting all your email address form fields to type="email" immediately. Virtually no one will even notice, except iPhone users, who probably won’t notice either. But the ones who do notice will smile quietly and thank you for making their web experience just a little easier.

You should run, not walk, to go read the rest of the chapter. But only if you are into HTML.