No problems with the upgrade here. I'm still playing with the new features. ZCO testing didn't go to well with our Windows admin person with Outlook 2010. Might have to wait another release or two on that. Also, I haven't figured out what you need to do to see the extra distribution list features for choosing who can send to a list. Although, I really still want a Mailman type moderation instead.
Other than that, much speedier and prettier!