That's one thing I really liked about ES, too, is the UI. I'm still getting the hang of things, but they really did well on the UI imo.

My guess is that its the best from various games, like Civilization 4/5 and Master of Orion III (the parts that didn't suck). I also saw some from Ascendancy if I'm not wrong. I also suspect the UI is not fully skinned yet.