The development platform features a new character animation system (made possible by Unity's acquisition of animation tools company Mecanim), DirectX11 support, exporting options for Flash, a preview of game deployment to Linux, and more.
Unity has billed the 4.0 engine as one that will make it possible for even small studios to create AAA-level titles, thanks to a promised boost to visual fidelity made possible by the platform's new features (e.g. real-time shadows on mobile) and optimizations.
Already purchased Unity 4 pre-order, great news though for everyone waiting on the new release, should help ramp up discussion and forum activity on the new bits - gratz unity folks!
Just a heads up for anyone installing 4 Beta that has 3.x installed, rename your 3.x Unity folder first.
And thank you, Unity Technologies, for also recognizing our Linux community as well.