Unity isn't fully cooked yet, but as we're approaching Ubuntu 10.10 beta, it seems like a good time to jump in and start taking a hard look at it. Also, I've been hearing a lot of good things about it so I can't resist the urge to go check it out for myself.
First impressions: shiny. Yes, it neat and modern looking. Unfortunately, I've seen enough things like that only to later realize how completely non-useful they are after trying to actually use them, that I'm now mistrusting of "shiny" things. But to be fair, I see a lot of things that make sense. The "dock" for lack of a better term, that stores default application launchers and icons for currently active applications is on the left side of the screen, which makes good use of horizontal screen space that is normally plentiful. On netbooks, for which this was primarily designed, vertical screen space is often at a premium, so elimination of the bottom bar is a good thing there.
The top bar is still around, but sadly has become very mac-like. Application menus, for most applications at least, seem to be on the top bar rather than in the application. I hate this, but to be fair, that's because I think it's too mac-like. I've never been able to "get" Apple's philosophy on UI design. However, I understand that doing this accomplishes a similar goal as above - to make better use of vertical screen space.
There are a few rough edges that I suspect will be worked out before release, but all in all it's not to bad. The virtual desktop switcher is just cool. There's also an application menu with search. I'm kind of undecided on that one. I miss being able to press alt-f2 and launch an application. Perhaps a hotkey could be assigned to automatically bring up this application menu, or maybe it has and I just haven't found it yet.
I'll keep it as my default desktop for the week, and see how it shakes out.