The new UI concept that you can see in X3: Terran Conflict was designed by one of our artists, Christian Vogel, and implemented by Michael (aka BurnIt!) and myself. At first we were unsure if we should implement it since it's a radical change compared to X3: Reunion... but after all, X3: Terran Conflict is more than just an add-on, and the improvements over X3: Reunion are so enormous that we just had to try it.
In X3: Reunion there are three separate menu systems that have evolved over time: The big standard menus, the so-called quick menus at the bottom, and the icon menus in HUD and in the sector map. For X3: Terran Conflict the standard menu system has been overhauled and the rest has been replaced by the sidebar and context menus. You will also find that there is no such thing as a big "ship menu" or a "station menu" any more, which have been rather central menus in past X games. Now ships, stations, and other objects "only" have unified context menus, which allows for much quicker interaction.
Another important change is the new mouse control. You can steer your ship by pressing the left
It's still possible to disable the mouse cursor and steer the ship directly with the mouse as in earlier X games, this is what we call the classic mode. In this mode the left mouse button is also available for control mapping, in case you want to fire with the LMB.