First off, I have greatly enjoyed this game, and have but roughtly 6 hours in so far.
There is one thing that is slightly annoying, even though it is my fault - a few times now I have finished a map and hit "exit" which takes me back to the desktop, when I intended to go back to the menu. This is my mistake and a mild inconvenience, but I notice that my games do not save when I do this - the map is as if I never played it. I was somewhat surprised the game did not save your state when the requirements for the map were finished.