I saw a tweet today referring to the MVCHTML5 helpers on Codeplex. I'm wondering if
I would definitely recommend checking it (I am a little biased as I wrote it!). But it's just a simple DLL that you include in your MVC project and it will give you all the benefits of HTML5 input types. If the browser doesn't support it - it will just fall back to a normal textbox.
To answer your questions though, it only adds a benefit if you are looking to add HTML5 functionality to your application or website. It uses the exact same syntax and the normal HTML helpers that ASP.net MVC comes with, but this just makes life easier if you are looking to add HTML5 functionality to your site.
Here is another link regarding HTML5 and the input types: http://diveintohtml5.ep.io/