Even going back to the old content isn't a pain, as it still holds up under scrutiny. The new areas, though, feel more alive - you're part of a grand operation, with many smaller sub-objectives to complete in order to achieve victory. I am largely happy with this.
Overall, I'm of mixed feelings about this game. I stuck with it for the long-haul without feeling like it was chore, but there's a whole new-game-plus section to the game I've not tried, and I'm not sure I want to see how it changes things, even though the Steam Achievements spoil some intriguing ideas. I might be content to leave it, as the issues it had failed to capture my heart, even with the charm it had.