I've played 6 or so two player games now. Its quite quick. You can manage 45-60 minutes once you know what you are doing. And yes, its great 2 player.
As the buildings are refreshed after each buy, the biggest difference between 2 player and 4 player is more competition for the Epic buildings and the Jump-starter buildings (as we call the Star and Key buildings respectively). Some of the Epic/Star buildings are very powerful, so there is more blocking in 4 player. 2 player is more friendly.
In 2 player you are also involved in every turn, as when it is not your go, you are reading the story points.