I am...confused.
I have to add my name to the list of people asking: Is this a new editor, a new engine or a new editor and a new engine?
Whatever it is looks nice and seems to be more functional than the current editor. I like the integration of workflow into it.
Would I be able to run a server on a linux box in headless mode? If not, the server hosting functionality isn't much use to me personally. I don't have any spare windows machines floating around
As for whether I'd buy it or not:
If it's a new editor, then I suspect my answer is 'no'. There aren't really enough cool/new features for me to justify spending $100 on it (let alone $200). Even if there were enough new features, I'd probably be asking "why aren't these features in the editor that I already paid to get a license for?".
If it's a whole new engine that's been made, then I would decide how the upgrade cost compares to the cost of moving to another engine. I'd then compare the features of the new Esenthel engine with those of other engines. One of the reasons I moved to the Esenthel engine in the first place was that the updates to the core engine were said to be free. If the updates stop being free (even for "really cool" changes), then I may be better off buying a different engine.