It also sheds a lot of the historical computer algebra baggage of Mathematica -- palettes for entering equations and so on are gone.
And although it doesn't support this yet, Wolfram Desktop will soon let you connect straight to a cloud kernel. It'll be really cool: you'll write ParallelMap, and (say) 32 kernels in the cloud will be summoned for you.
And what about the Discovery Platform and Data Science platform? How will these differ from Mathematica?
The emphasis in Discovery and Data Science platforms will be around workflow and reporting, though the features there haven't been finalized yet.
Playtime! Awesome.
I'm just a Home Edition user, but as long as the upgrade price starts with a 1 then I'll be paying up.
That is, if you can tell me you've fixed undo in Notebooks :)