My experience with HTML5

In 2010, I helped move my employers standards to recommend using the HTML5 doctype and new HTML5 semantic tags wherever possible. As tags like <header> and <footer> were introduced to fit modern website builds, it makes a lot of sense to the average front-end developer. See Go Give Leo for an example of a recent site built on HTML5.

I'm also a fan of the HTML5 doctype because it appears to be more robust than past versions of HTML (HTML4, XHTML) - in the sense that it validates under circumstances where it would not have in the past.

New form elements and attributes in HTML5

I've been using input types like "tel", "number", and "email" for some time - the small validation and usability benefits are worth it, and it falls back to type "text" for older browsers. A few other easy wins are "placeholder" and "Required" attributes.

Rich animation with the canvas tag

Though not a good idea for semantic content, the Canvas tag is great for rich animation and interactive content. I've done some initial explorations into programmatic drawing in canvas, one example being my html5 particle system.