I just finished reading Danny Ayers's ramblings on MicroFormats, and while he comes out a bit conflicted, it in some ways helped me get a clear view of my own position on it:
MicroFormats using XHTML is to me what tables for layout was to older HTML.
It is a semantic overloading that tries to apply meaning to tags far beyond their original intent, and while it is tempting because of the immediate advantages, I believe it will come back to bite people badly.
One of the claims that often props up is that the main advantage of using XHTML is that it is immediately stylable via CSS, yet the current main browsers have no problems styling plain XML. A quick look at my feed (via Feedburner) demonstrates that - Feedburner have done a wonderful job of it.
If you need any more, writing cross browser javascript to use XSLT to transform the XML is trivial - my first attempt, which was also my first attempt at using "Ajax"/XMLHttpRequest etc. and my first real javascript app, took me less than half a day to throw together. For that matter, if the page returned is static, specifying an XSL stylesheet works great across at least all Mozilla based browsers and IE if you're a little bit careful about how you write your XSLT.
I just don't buy the convenience argument. I find a well defined XML vocabulary much more convenient, because it is often a lot clearer what the data represents.
Personally I'm becoming a fan of GRDDL, because it allow us to pick simple XML syntaxes (or for that matter those obnoxious Micro Formats) and have an automatic way of deriving RDF, so that we can use the most convenient and most expressive syntax we want in the main document.
I'm increasingly moving towards using XML + XSLT for publishing documents online as well. My first experiment was an online change request list for team at work - instead of maintaining an HTML version, I moved to XML + client side XSLT conversion exclusively. Works great, and resulted in a significantly smaller page (not that size matters for that particular application).
XHTML for me is mostly something to be generated from other sources, not something I'd want to use as a source of document data itself anymore.
As such, the Micro Formats seems to me as a distraction at best, a repeat of huge mistakes of the past at worst - instead, please give me a well defined XML vocabulary; and if you must, please just write some XSLT to generate the XHTML.
Glad I got your trackback ping, HTML tables is a strong analogy. I'm still conflicted (perfect word as well, thanks), in part at least wondering if pointing out the failings of microformats will make any difference in the long run. I generally have the same preferences as you describe, but am less optimistic about your request for a well defined XML format (and my version would be "please give me RDF/XML" ;-)