These are very welcome improvements, especially in the area of adding a parsable semantic structure to pages.

My personal favourite semantic additions are:

1. The itemtype, itemscope and itemprop attributes, for completely unrestricted noun-based semantic markup (especially useful when using a standardized set of information schemas, such as those provided by http://schema.org/),

2. The <time> element, to allow easy parsing of time no matter how it is visually displayed, and

3. The <figure> element, which encapsulated pieces of media with their captions, much like a LaTeX figure does.