Poked around in it a little more. As expected, the issues that jump out at me are mostly related to newly added features, or plugins.
The plugins that I've noted small issues with include contextmenu, vacation, help, and compose_newwindow. Most of these are small css bug, I suspect.
New features that cause problems - the buttons at the bottom for threaded view options are still red and overlap the other bottom controls.
Other missing items - no tool bar entry for "Mark messages as..."