Microformats add semantic value where HTML fails to do so. Improving semantics means consumers need to make use of them so examples would be:
- A custom user.css in Firefox that highlights hcards and floats it for easy reading.
- A customer database application that can read an address in microformat, saves typing it.
- A calendar can load an event that's listed in microformat with one-click.
The idea is that since there is no <street> element in HTML, using a semantic hook like <span id="street"> means user agents can process the information more effectively.
How microformats will evolve is uncertain as HTML5 is still being argued/written and the semantic nature of the language is up in the air, but one things for certain, using microformats gives more people more options to consume the information which can only be a good thing.