I ran into an issue in 2006 because a coworker was clever and used a "date" input for a date. Most browsers just ignored it, but I was using Opera which implemented Web Forms 2.0. While I got a better experience (with a nice pop-up date picker), the form put the date in using the wrong format and his code couldn't read it.
Placeholder is great. Found this for Django: <a href="http://github.com/rhec/django-html5/blob/master/html5/forms/widgets.py" rel="nofollow">http://github.com/rhec/django-html5/blob/master/html5/forms/...</a> (however it looks shallow; I already spot that EmailField doesn't subclass the old EmailField which as server side validation). Would like to see these with their respective server side validators.
A colleague of mine (Eli Van Zoeren) wrote a jQuery plugin that lets you use these new capabilities:<p><a href="http://www.newmediacampaigns.com/page/nmcformhelper" rel="nofollow">http://www.newmediacampaigns.com/page/nmcformhelper</a><p>In browsers that don't support features, they are emulated in javascript.
There is also an experimental version of datalist in Opera (and possibly other browsers). Demo at <a href="http://html5.org/demos/dev.opera.com/article-examples.html" rel="nofollow">http://html5.org/demos/dev.opera.com/article-examples.html</a> (only the first one seems to work in latest Opera).<p>Full article at <a href="http://dev.opera.com/articles/view/an-html5-style-google-suggest/" rel="nofollow">http://dev.opera.com/articles/view/an-html5-style-google-sug...</a>
Minor internet correction, the placeholder attribute has actually been in Safari since 2003. Also, Safari has supported range inputs for quite some time to.