I have never tested it. One thing it would do is increase your code size which I don't like to do. It would be interesting thing to test. It would be cool if Google were to understand microformats. Specially for date specific data and addresses. I don't think it would hurt.

We've had a couple of threads about microformats [google.com]. I'm surprised they've been around so long.
They don't seem to have much SEO impact yet, but they can be good for the accessibility of your users.

I've looked at this up and down as I have a site which would suit the use of microformatting particularly well.

But for now I can't really see what additional benefit it would offer users but I can certainly see how it would be of great use to anyone wanting to scrape my content. Sure they'll do it anyway, but this gives it to them beautifully formatted and categorised to do with as they will. It's be like handing over the entire database to anyone who wanted it. Am I missing something?

Information form professional would be appriaciated