Dave Winer has asked the community for some nitpicking on his OPML 2.0 spec. I'm giving it a shot.

• Is it possible to make the jump from RFC 822 dates to ISO 8601 or is it too late?
• Could you specify which email formats are valid for ownerEmail attribute? 'mailto:randy@kbcafe.com', 'randy@kbcafe.com', 'luksa@dallas.example.com (Frank Luksa)', etc.
• The text attribute wasn't required in 1.0, but is in 2.0, which will invalid some feeds which were previously valid.
• The category attribute need an example. I think I understand, but there's too much room for misinterpretation.
• Could you say that the htmlUrl attribute must be a URL or something like that?
• What are the valid values of the language attribute?
• Please provide the known value of Atom feed version attributes.
• In inclusion, you rely on the file extension .opml when processing an element. I suspect this will prove problematic. Why not use a type='opml' attribute instead.
• In extending OPML, you say that extension element AND ATTRIBUTES can only be used if defined in a namespace. In OPML 1.0, you were allowed to add any attributes to outline in the OPML namespace. This will cause some 1.0 feeds to be invalidated by 2.0.
• The description attribute in 1.0 often contained HTML markup, but according to this spec, it may no longer contain HTML markup. Could we add a bit of text to specifically allow HTML markup in description.
• Requiring auto-disco to use rel='outline' invalidates most existing implementations of OPML autodiscovery. Maybe the value SHOULD BE rel='outline', rather than IS.
• Can you add a section on the OPML extension namespace.

http://www.opml.org/spec2