But you can continue using <input type="text"> if you prefer to. Remember HTML5 is new; no browser is even close to fully implementing it yet.
I agree that the logical thing would be to check the validity of the email, but I am not sure that as a developer I want to leave this responsibility to the browser.
You will still be able to use your own custom validation js routines instead, if you want to. It's up to you.
I understand the idea of semantics and their understanding by machines, but to me, this is work we're doing for G and the other SE, and not for our end user. Anything you don't do for your user is useless.
Think about it: we could just use <span>'s and custom classes for everything. Why don't we do this? Parsability, maintainability and accessibility. But if you don't want to use the new structural elements, that's fine too.
Except that if you don't do [use HTML5], your site will start dropping in the SERPs.
There are loads of completely-baseless SEO rumours out there already. I really don't think we need to start any more... :)