Well, I finally picked it up 2 days ago. I finished it yesterday. Its way, way too short. It lacks any real semblence of a story. While going back to some of the AC standards (laser weapon, giant aircraft boss, flying through tunnels), they missed some of my favorites, such as real naval assaults and some great cityscape battles.
Comparing Zero to 5 is like comparing Jedi Academy to Jedi Outcast... but then, neither 5 or Zero were what 4 was. Still, I found a whole lot more meat in 5 than in Zero. Its like half a game, and I wonder if that doesn't have something to do with the price.
Course, I still love flying these damned planes, but its just lacking anything for me to really sink my teeth into.