Very excited about the new release! This is the first time I have installed and really worked with 3.0. Here are a few thoughts about my experience.
I hope these comments are helpful and in the correct forum.
Overall
Very clean and easy to work with. It will take a little bit to quit looking for the new button in the upper right corner.
Main Admin Menu
I love how the top horizontal menus work. The control panel menu is always at the top and the when on the Edit Article screen the Save menu moves up to remain just below the control panel menu. Very cool.
Menu Manager: Menu Items
text in the search box gets cut off
Words Ascending and Descending are cutoff. I think a slightly wider dropdown and they will show without the "..." I think you could narrow up the "Sort by table" and widen the "Select the ordering" dropdown and the upper right corner will look a little cleaner and easier to read.
Dashboard
Would be cool to see a section displaying the required joomla / extension updates. This way when the admin first logs in they are made aware of any updates that need to be applied.
After looking at the dashboard a little more I did notice in the lower right corner a "Joomla is up to date" item. I am not sure how much priority this item should be given.
One suggestion:
Settings (upper right corner)
It would be cool if the "Clear Cache" and "Purge Expired Cache" items cleared the cache instead of being taken to the page where I have to click a few more time to clear the cache. I am thinking of the functionality of the NoNumber clear cache plugin.
Hope this helps. I am very impressed with the new user interface and happy to do more testing and reporting if this is the type of information you are interested in.
Thanks! -- Steven