The best thing about normal maps is that they can frequently be used INSTEAD of extra polygons and still look better than them (while keeping the polycount down and the framerate up).
not buying that... play any mission that has at least 3 cap ships with normals and you'll see the FPS going down right away.
Uh, dude, this doesn't make any sense.
You're comparing 'ships without normal maps' to 'ships with normal maps' when you should be comparing 'ships with normal maps' to 'ships with all the details provided by normal maps, except rendered as actual polygons instead.'
THEN your computer would be crawling. Normal maps really boost efficiency.