Let's see. 1) New standard shaders 2) Random editor UI garbage 4) Webgl, finally 5) Some multithreading 6) More of shit you wouldn't care for And as a minor mention, PhysX upgrade from fossilated pile of shit to merely outdated.
How about better input API? I would certainly appreciate that. Having full thread-safety would also be a lot of help. An integrated C compiler and C API certainly sounds like too much to ask for, not to mention using Unity engine as a framework in your C++/whatever app.
It certainly is better than the last version, but it still needs a lot of fixes.