MaleShep: Soldier. FemShep: Infiltrator. Infiltrator is harder to play as during the combat, especially since I don't have the weapons I became accustomed to as a soldier. One day I'm going to go back and play all the way through ME1 and ME2 as an adept and see how different the combat feels with no military training.
And once I finish a couple more N7 missions I will have done EVERYTHING and be ready to start the endgame with the Reaper IFF mission!
The action and the stage designs are way improved. The interface is way improved. The Mako bits are gone (though planet scanning is really tedious it can also be a little relaxing after a shoot em up). The inventory system is fixed.