To my expectation-- and delight-- the gameplay was very similar to Ace Combat games that predate Assault Horizon.
Zip around in fighter planes armed with 60+ missiles, maneuver to shoot down other planes, bomb targets on land & sea, avoid missiles, and protect assets in escort/protection missions.
I personally didn't care for the Enhanced Reality System or [Assistance-]OFF MODE, and did not use them outside of the two missions that absolutely required the player to use them.
The game seemed to favor the 3rd person camera. It was the default view. I prefer dashboard/cockpit views in my air combat games, and OFF MODE forces the camera to a 3rd person perspecitve. Kind of an immersion-breaker there.
Disappointingly, this means it is impossible to perform a manual stall as a tactical maneuver in the first person view.
A rather major complaint I have with the cockpit view is that it is missing the pitch/roll and bearing indicators on the dashboard HUD. Instead, it is completely blank! This requires the player to actually use the artificial horizon and compass on the instrument panel.
While this may seem like a good idea for immersion, they are hard to quickly read at a glance and are different on every plane. That's appropriate for an in-depth flight combat simulator, not a more arcade-style flight combat game like HAWX. Even then, the HUD on the dashboard would display that information for a pilot.
Additionally, airspeed and altitude are displayed on-screen anyway, so it's not as though they left out the pitch/roll and bearing indicators for immersion. So this seems more like a mistake than an intentional game mechanic. This was not fixed in HAWX2, from what I've seen in screenshots.
Thankfully, the game has a "flying camera" perspective similar to Ace Combat's default view, which displays pitch, roll and bearing in addition to airspeed and altitude.
The plane variety was more than adequate. Overachieving, even. For instance: The SR-71 'Blackbird' is available, but no missions require its specialization; Strategic Reconnaissance. Though I suppose it has no place in any flight combat game, what with being an unarmed spyplane that was effectively replaced by satellites.
The story was rather lackluster. No character development of the wingmen, no fantastic superweapons to conquer, and the final mission didn't feel like a final mission at all. Maybe this is just Tom Clancy's flavor of "real fiction", or maybe Ace Combat's strangereal world events set my expectations too high.
Overall: TOTALLY DECENT, and the best Ace Combat clone I've played thus far. However, I found it rather difficult to not constantly compare HAWX to Ace Combat. In fact, I dare say that my single favorite thing about HAWX is that it made me decide to whip out my PlayStation 2 and replay its Ace Combat games.