Lets compare the coding workflow in Unreal Engine 3 and Unity 3:
In UE3 you play the game, find something you want to change. So you shutdown the Game/Editor and go to the code. You code in some immature language called UnrealScript (I think there is a complicated way to use C++ too). Then you compile. Then you startup the Game/Editor again (this is slow).
Also the engine APIs are one of the best software designs I've seen in a long time.
And, naturally, there's no way to turn it off. Strictly speaking there is but it requires restart of Unity, not just the game, to reload code. Which is basically the UE3 workflow you describe.
You're right though; there are quite a lot of good parts of Unity - which is why I'm sticking around for now.
But I stand by my assertion that their focus on headline features is troubling.