Seeing as the X2 air combat is currently almost exactly the same as the X1 air combat, I can see how people would be dissastisfied with it. The esstial thrust of air combat in X2 is either:
1) Run straight at your opponent
or
2) If you have more than 1 aircraft, kite your opponent into revealing the section of UFO that is uncovered by weapons and start shooting
I spent quite a lot of time making air combat more interesting in X1, resulting in three generations of Flying Circuses, and I'm sure Charon can recount his experiences of changing up air combat for X-Division. In my case, what I aimed to do was create an interesting puzzle to crack. Each new UFO presented a different type of challenge. Perhaps it fired swarms of micro missiles. Perhaps you had to fly between multiple turrets. Not all my creations were successful. I think that if X2's air combat is to be more fun, it needs to create new problems of positioning. The rotating turret and energy shield are a good start but there's a lot more that I feel could be done.
Firstly, I think that Goldhawk should steal Steambird's control mechanism for aircraft. The mechanism that the original Steambirds uses is an excellent fit for X2's air combat. You can see the turning curve for your aircraft and plan for where it's going to end up without constantly hitting the pause button every few seconds. When the aircraft reaches the end point of its planned movement, that's when you can set up the next plan. I can see this being useful for also setting up and controlling multiple aircraft at once, as you could bandbox aircraft together and set them all by the same plan.
Secondly, I think Goldhawk should take a leaf from shmups, specifically the boss fights in shmups. As frantic as Boss fight shmups are, they are all about positioning and that's made possible through the wide range of projectile types that bosses have. As things currently stand, UFOs have two types of projectile - homing and non-homing. There's no continious beams, no aerial mines, no splitters. no swarmers. There's no telegraphing, no wind-up, no obvious lock-on. I'd like to see more projectile types that encourage positioning, because, at the moment, they don't, really.