I just installed Lion. Installation took about 40 minutes on my Mac Pro.
My first impressions
The system has so many new features, I don't know where to begin! By default running apps do not have the blue point under their icon. This can be activated in the Dock preferences.
Mission Control is actually great! I love the way it combines the dashboard, all apps running in full screen mode and spaces on the top section. The middle section shows all running apps with their open windows. Please note that the Dashboard can still be accessed by pressing F4. By pressing F10 I can still see all open windows for a specific application.
The plus icon on the top left of every window behaves exactly the same as in Leopard. It doesn't invoke the full screen mode. iCal, Safari and Mail have a full screen mode option under the View menu. Actually I prefer it like that.
Scrolling with inertia on is strange. I changed it to the Snow Leopard default setting. This isn't a touchscreen device, so scrolling should work differently.
The new gestures are really great, especially if you have a Magic Trackpad. I can use three fingers to swipe through the open apps. I can invoke Mission Control (with three or four fingers), show the open windows of a specific app (just like pressing F10) just by using gestures. Great stuff!!!
If you have a Magic Mouse then the gestures are not that many, but you can still change between all apps and open Mission Control.
Safari is for me the biggest feature in Lion! The full screen mode combined with the double tap to zoom feature (borrowed from the iOS Safari version), make it really great. Text scales very nicely and with the Magic Trackpad I can also zoom in and out. It feels like using Mobile Safari but it is much better
Safari is also much faster than before. I open Engadget.com and it finished downloading in 1-2 seconds. When I reverted back to my Snow Leopard installation I immediately show the difference on Safari and Chrome.
The new two finger swipe gesture in Safari is also great. You can go back and forth between the sites you have visited. Great!
Mail has also received an update. The new view works very well. There is also a new flagging system. Now flags can be set that have different colors. It is almost like using Categories in Outlook.
Addressbook is almost exactly the same as on the iPad.
Using the Launchpad is also nice..I never thought that I would like it.
The only thing that I found strange, is that the only way to create a folder is by dragging an app over another. (just like in iOS). There should be a + symbol that allows you that.
The system is of course not ready for prime time. I had a crash when closing Mail. I also installed Skype but it crashes every time I try to login.
The new Finder is also nice, but I don't really like the new icons.
Preview is great. It opens in its own window and it seems to work much better.
Overall I am really excited about this release. It seems that Apple is doing almost everything right and the Lion will roar!