Well, Symbian Anna is an evolution of Symbian^3. It fixes most of the things that were annoying in Symbian^3 and also adds new features that were missing.
One of the most expected and needed updates is the text input. The Symbian^1 alphanumeric keypad was inherited by Symbian^3 without notable improvements, but Anna finally changes that. A full QWERTY split-screen portrait and landscape keyboard is available now, and it is used by most of the applications. There are times when you find yourself in the same situation as with the original S^3, in a full screen input dialog, but that one also has the portrait QWERTY enabled. I'm sure it's just a matter of time, before all apps will use the split screen keyboard.
The full QWERTY is not the best in business, but it does have some features that other QWERTY keyboards are missing, like the editing menu, or the arrow keys for moving the cursor around.
Another big change is the icon theme, which is the same icon theme used on MeeGo, where icons are square with very well rounded corners. The icons for folders are more visible, and things are not as confusing as the were with previous iterations. The folder icons are filled with a single color and have suggestive imprints over them. In other words it's almost impossible to mistake a folder for an app with the new Symbian Anna.
In the settings menu, and most of the apps provided by Nokia, the list icons are now monochrome, bringing a more minimalistic look to the icons.
Another big improvement is the speed of the homescreen and the way the widgets are refreshed. The swipe gestures on the homescreen lead to immediate homescreen slides compare with the old version where you used to swipe left or right and after a fraction of a second, the homescreen would scroll over.
Th widgets show a loading circle when they are refreshing so you know what happens with them at all times, as opposed to the old way where you had no idea a widget was refreshing until it actually finished.
And the improvements do not stop here. Some applications got notable updates, and here they are.
The calendar display includes the events for the current day as well as the full month view. A nice touch is that now the month view has pinch to fullscreen. When you pinch in, the full month view shows on the entire screen, and if you pinch out, the month view also shows the today events too.
The calendar got another improvement in the form of the new event dialog. It's now easier to add and configure a new event than it was on the previous version.
The file manager was pretty good to start with, but now it has a new feature, that was very much needed, the mark multiple items. The file manager switches the view to checkbox selectable items, and you can mark as many items as you want by just touching them. The file manager still misses the range mark ability, but it's still very usable. In other words you may not need an alternate file manager again.
The browser got a huge update. Nothing about this new browser reminds you of the old Symbian browser. Even if the user experience is still a bit clunky, the browser is far better that it ever was on Symbian. The speed of the page loading is better, the address bar is new, and the menu is better organized. You have a soft back button which is very helpful in many situations, and you can open a new window whenever you like.
The contacts application was also updated, and the search trough contacts is done now by typing on the QWERTY keyboard instead of the old alphabet that was popping out on the old version. This kind of search seems more natural than before.
In addition to the usual application package, Symbian Anna comes with the topApps application pre-installed. The topApps application gives you a hand in deciding which apps you should download to your phone, have three categories, Featured, Staff picks and Reviewed. The user interface is similar to the Ovi Store interface and it is a good place to start when you're looking for applications.
All in all, Symbian Anna brings more background changes, in terms of optimization and speed, than user interface changes. It removes most of the nags that Symbian^3 inherited from Symbian^1, and if you compare Anna to S^1 they don't seem to be from the same planet.
It's pretty clear to me that Nokia is preparing for Symbian Belle later this year, and by the looks of it, it will change the way we perceive Symbian in a big way.
Good job Nokia!