I've been using Unity as my primarily shell for the past week, in Ubuntu 11.04's current beta (fully updated). This is a probably boring description of my impressions and some ways it could be improved. I could suggest the changes through launchpad, which I haven't used for that type of thing. I haven't done it yet due to concerns that I would do something wrong.
I like it when a window is maximised because it combines the panel, the menu bar and the title bar into the one bar. This is very good for saving space and I like it when I'm just browsing the internet with one maximised window. Seeing the indicators apparently within the title bar is like the wingpanel idea.
Maximising also makes the launcher (dock) disappear, which is good for saving space but I want to be able to see what I have open. I would like to have the option to not have the launcher autohide to solve this. Or have some other indication in the panel.
When I have multiple windows of the same program open, clicking on the icon for it on the launcher makes all of its windows visible similar to how GNOME Shell does when pointing to the top left, except the only possible interaction with the windows in this mode is selecting the one you want. IIRC, in GNOME Shell you can press buttons on them in this mode. It should be changed to allow that to happen. If I want to close one of them, I need to select it first.
Also, the menus (of the menu bar) are hidden behind the title when a window is maximised unless the cursor is over the title area so it's a bit of guesswork where to point the cursor. It's no longer a beeline to Tools, but an "L" with a change of direction around Help or Bookmarks. But this isn't something I really notice.
When a window is not maximised, the menus are over the name of the program (it looks like "Firefox We[fades out] File Edit"....). that's not the title bar, as each window has its own when minimised. The global menu is of course disassociated from the window when it is not maximised. You have to select a window for that program's menus to show there, which is an annoyance when there are several windows on the screen.
The overlay scrollbar has grown on me. It would be improved if the control would be able to appear not just where the narrow scroll position indicator is, but anywhere along where it can be. It matters because if you click on the controls, it scrolls accordingly and keeps the controls still as it should, but if you move the cursor slightly away, you can't just move it back to where it was a second ago and find the controls appearing again. You have to move to the scroll position marker. Also, some default applications have the old scroll bar. Firefox and Gwibber, at least. It looks unprofessional to have different scroll bars.
Also, I have the Dust Sand theme and my close/minimise/maximise buttons look completely different when maximised.
It's a lot more stable now.
