Symbian^1 is essentially N97 UI, Symbian^2 would have been the first real OS repackaged by Symbian Foundation, but it was meant for manufacturers that where already been using 5th edition(so Nokia, SE and Samsung). In the end it was left out by the manufacturers.

Symbian^3 is graphically superior to any other Symbain release and is a big jump from Symbian^2. It will be rather eye candy heavy UI when it comes to effects. When it comes example kinetic scrolling i honestly think it will be great with Symbian^3.

Yes i'm a big Symbian fan so i'm very interested to see Symbian^3 in action on N8 or E7. Thought not really interested to see it inside N900.