Having seen both parts at the Chicago premiere, I have to say I don't think it was a good idea to have them a week apart. Part 1 just feels so ... insubstantial without Part 2 coming right after. They should have made it a 2-hour premiere instead of a 2-part premiere.
For the record, as a single 2-hour "event," as it were, I thought it was very good. Though I have to say, anyone starting the show with The Impossible Astronaut would be incredibly confused.