Alright, I've played with it, and read the instructions from the Help icon on the Launcher. I've been at it since it was released on April 28th. Let's talk about it.
At first, the Unity desktop is clunky compared to Gnome's menu set up of Applications, Places, and System. Having used the Gnome menu system, not having that, initially in Unity, made me feel lost. How do I find that little used application that you need just when you need it? With the Gnome menu system, you know exactly where to look for it, for example, Inkscape, for me, with the mouse, was always at Applications>Graphics>Inkscape, quick, easy. If I'm using GnomeDo, it's Super-space-in.
And here's where things start getting interesting. If you switched from the Gnome desktop with GnomeDo, you'll find that GnomeDo is still on Unity, but only at start-up. If you hit Super-space in Unity, you get the Launcher. You can still use GnomeDo, but you have to change the launch key to another key in GnomeDo preferences at start-up. Ctrl-space, will do the trick. GnomeDo now works in Unity.
What about the Unity Desktop navigation? Unity took over the Super key for starting the Dash and Launcher. If you press Super key and hold it down, you get the Launcher with numbered icons, hit a number, and the application starts. If you press the super key once quickly, you get the Dash, press it again, the Dash goes away. Press the Super key for the Dash, and start typing "ink," hit enter, you start Inkscape.
Applications can be added, or removed, from the Launcher from the right mouse click menu. You can rearrange icons in the Launcher by dragging them to the desktop and then dragging them back to where you want them.
If you bring up the Dash, the screen that takes up half the desktop, and start typing in the search window, applications come up divided into various, but not consistent, rows. The most used applications are in the top row. But rows change as you click around, and are not always laid out the same, which is confusing.
If you want to customize Unity, you'll want to install, via the Ubuntu Software Center, CompizConfig, the Compiz Configurations Settings Manager, which can be brought up either through the Dash or in Systems Settings. After installation, the size of the Launcher icons can be adjusted by going to System Settings from the upper right icon, then CompizConfig Setting Manager under Personal, then clicking on Ubuntu Unity Plugin, and then clicking on the Experimental tab. But that's only one setting and it seems like settings are all over the place, instead of in one place.
When your in the new Firefox 4, Ubuntu's standard browser, and you go to hit the back key, but go a little too far to the edge with your mouse, the Launcher will appear over top of the back button, which is frustrating. You have to back away from the edge, wait for the Launcher to go away, and then carefully go to the back button.
The Dash doesn't need to take over that much screen real estate, there should be a way to adjust the Dash size. My monitor is rather far a way from where I sit in my recliner, so I use large font sizes for better visibility. When I first saw the Dash, some icons were off screen to the right. I had to reduce the system font size to get the entire Dash in the window.
And now to the Super key, too much functionality in one key. If I hold it down steady, the Dash appears, sometimes after an annoying delay, if I don't want the Dash, I wanted to tap the super key and get the Launcher instead, you have to wait for the Dash to disappear to try again. Of course, you can use Alt-F1 for the Launcher, and by the way Alt-F2 gives you a Command Window, but in general, the Super key is flaky, sometimes it works properly and sometimes, you either key it wrong, or somehow the expected outcome is different and always annoying.
By design, the top menu bar is not there, including in applications. I can think of one application, the Gimp, where this is downright onerous. There should be a way to allow the top menu to stay on screen. There probably is, but I haven't found it yet.
Then there's the difficulty, and lack of configurability of the interface. I can change some items, but not others. Canonical needs to have an easier way to configure Unity, with more configuration options, all in one location.
Given I can customize the Launcher, I can see where this would be an easier interface for the mouse user, but for the keyboard user, usually the person doing development, and users that don't like using the mouse, the interface is still too clunky for my liking. By clunky, I mean the above mentioned quirks.
For the person, and especially heavy keyboard users, who are use to Ubuntu Gnome, who have followed Ubuntu through many releases, to ask these users to stay with the Unity Desktop, to stay with it and stick with Unity, this is a frustrating learning curve. With GnomeDo installed in Unity with a new start key, it would seem folks would just go ahead and keep using GnomeDo as their Launcher, as they always have. And if that's the case, why not just stay with Gnome. Canonical has its work cut out for it, by next release date, if it plans not to give users the ability to switch back to Gnome.