HTML5 defines various semantic tags to mark your data:
It also allows for custom data attributes starting with "data-"
within elements.
There is support for microdata which is based on microformats to provide more semantic structure to individual and groups of elements.
And to answer your main question:
No, I don't microformats because I didn't see the advantages until I gave your question a serious thought. I am using the newer HTML5 elements such as time, and custom data attributes, but not microformats because the data was already structured on the backend, and for more structured and semantic access, I'd would've used RSS feeds with specific extensions and include a link to the feed within the document itself.
That said, here's why I still support microformats and believe they are awesome and will most likely start using it in the very near future. For me, it serves a very specific purpose and has to do with programmatic access to the elements within my web applications. RSS and Atom feeds provide the same data in a very structured manner, but it's an alternative view. Microformats, or any other homegrown standards can be used effectively to enhance applications.
As long as the elements are structured in a standard manner, I can build upon a shared library of reusable code across all applications that deals with commonly occurring data items such as names, addresses, contact details, telephone numbers, etc. to enhance all applications. For example, automatically linking addresses to Google Maps, or linkifying telephone numbers to use a native protocol such as tel:
on the fly for mobile devices and various other enhancements that I can do.