Awesome
I loved the first one and this one just improves upon it drastically by utilizing the player created maps. You have taken the creativity of your players and given it back to us in what I would call a sequel and that, in my opinion, is the key to a great game. User-created content is becoming a part of the current generation all of these levels were fun, challenging and frustrating.
I can't say much about that graphics or gameplay because nothing has changed in that department since the first one. I hope that the next one has even more user content in it but I also hope you improve upon the graphics, the mechanics or the different kinds of building materials and objects. I'm not saying it needs to be changed because it is already great, I am just saying maybe you should add to it.
My only problem with it right now is that I can't share my maps, it keeps telling me to connect another time. I'm sure if you were going to fix it, you would do it in the near future. Overall, a great sequel or "expansion" to the original but I would like to see more units and objects in the next one.