Faultline is one of my favorite zones for story arcs. It has some of the best in the game. Even the "rescue fusionette" a character that comes off kinda annoying as she cant seem to stop getting captured, is done with some good taste.
The new mission maps here are a great change from the usual map missions that after playing the game for 3 years, ive gotten most of em memorized now. Its a pleasent change. and dont forget theres an easter egg room that was hidden in the zone that comes complete with a badge.