i've had microformats on my site for ages and never seen any noticable benefit. 99% of people probably don't even know that they're there.
i wish they would just leave it alone though. i thought people we're giving up on all that XHTML stuff with HTML 5.0 coming out, and now they're talking about another XHTML-only version of an HTML thing. if they keep doing that they are going to end up with two languages that do the same thing. it will be like PHP and ASP.