The Wordpress upgrade guide says:
Consider rewarding yourself with a blog post about the upgrade, reading that book or article you've been putting off, or simply sitting back for a few moments and let the world pass you by.
So, a post, then. I must say that the interface is going to take a bit of getting used to. In addition, the color scheme choices are... kinda muted. I liked the darker blue from previous 2.x versions, and high glare situations, I'm noticing that I can't always see the logical separation of the menu section.
Oh hey! I can switch back the old color scheme! Excellent.
The UI changes made to the post editor are excellent. I like the understated "Add media" buttons, and the additional AJAX functionality is useful and not overbearing, exactly how said technology should be used. The UI and font selections system-wide are great.
I don't like that they still haven't fixed the DST time zone thing.
Beyond that, not bad. The upgrade process went smoothly, and here I am.