Some excellent posts here, so far I agree with basically everything that's been stated. Without a doubt, the most significant issue that I feel is keeping this sim from achieving pure excellence right now, are the matters concerning the AI's unrealistic behavior. Personally, I feel this is the greatest immersion killer. A problem that resonates through both single-player and online co-op. And like Patrick's OP, I feel some of these issues are completely feasible to improve upon if they are given appropriate attention, like;

1) Superhuman AI scout gun accuracy in all regimes except when trailing from dead 6, where they are largely ineffective.
2) Superhuman AI gunner/turret accuracy, particularly from distances well outside of realistic effective combat ranges.
3) Superhuman AI situational awareness. They know where you are at all times when you're in range, regardless of their orientation or preoccupation with another opponent.
4) Superhuman AI visibility. With the exception of clouds, they can see through all objects to track the player's a/c and never lose sight of it.
5) No AI self-preservation or damage assessment to initiate RTB protocol.
6) Enemy AI's fixation on player's a/c regardless of accompanying AI wingmen or tactical situation.
7) AI wingmen's complete disregard for multiple AI opponents attacking player's a/c when they're not themselves engaged and in a position to assist.
8) AI wingmen's complete disregard for maintaining formation discipline or for executing direct orders.

These fixes alone would be a huge improvement on the entire RoF experience and open the door to a flood of immersive mission and campaign possibilities.

Teaching the AI basic and acceptable ACM on the other hand is a difficult proposition, but can also be accomplished, as has already been demonstrated by the work Team Diadalos has done with the 4.11 patch for IL2. Personally I believe that certain well scripted scenarios with some appropriate variability for AI pilot skill, a/c, and spatial circumstance could give a very convincing impression of AI understanding and reaction to a given tactical situation. Games from several different genres have managed to accomplish this in the past, and gave off the impression of superb AI, when really it was well executed script.

It's difficult to gauge how important 777 believes looking into the AI matter is. They've addressed a few issues already, and I'm sure everyone is thankful for that. However as far as I'm concerned, the AI issue should take precedence over a host of other matters. Obviously, priorities among players will always be split, and I also respect that 777 has a business model they believe will sustain them into the future... but I really feel they should improve upon what they already have, starting with the AI. As it stands now for me and the people I fly with, as impressive as RoF is in other departments, it's difficult to stay interested in it when these issues surface immediately upon first contact with the AI. It takes us straight out of the beautiful and convincing atmosphere that RoF accomplishes so well, and makes us feel like we're just wasting our time playing some console arcade game for the masses.

Anyway, that's my 2.