Very First impression: More pictures, Tinier fonts that cant be resized.
While the new font is fairly readable, the smaller size is a bit of an insult for my aging eyes. Not cool, and not changeable, as far as I can see.
At first, it looks like the navigation is very different, the sidebar that has been with us since iTunes 1 is gone, replaced by a ribbon which lets you choose content types and view a dropdown of your devices. Turns out that you can still turn on the sidebar, it’s an option in the View menu.
iTunes Match came up pretty quickly, and is no longer called out in the sidebar list. Device management features seem to be working better with my iPhone 5.
I’ve left my desktop with the old version and will post any interesting comparisons I find.
I have noticed some glitches in the way some of the screens load, where the HTML 5 layouts are either messed up or text fields are displaying with strings like “DI6.SortOrder.Featured” instead of the title “Featured”. I”m wondering if some instances of the servers are not syncd up. Apple runs iTunes on tens of thousands of servers, and restarting them for updates is not an instantaneous process.
Edit: Gruber has a pretty good summary of the new interface already.