There are differences in the way the different aircraft handle, but there's still a sense of genericness. I haven't played any mods, but ALL aircraft in the vanilla game have the same flap positions: Up, Combat, Takeoff, Landing regardless of what the historical planes had. This leads to the feeling of many aircraft being modeled the same. Engine overheats are overmodeled. I like that they tried to make the gauges more accurate, however some aircraft are also missing a few needles (the F4U's airspeed indicator, for example, had separate needles for both the inner and outer tracks, whereas in Il-2 you have one needle, making gauging your airspeed difficult). I don't like how you hear the radio chatter for course headings and altitudes for ALL flights in the area, not just your own. Confusing as hell when your orders are to head 240 at an altitude of 10,000ft, when the radio is blaring "Heading 159, Altitude 1." Which oh yeah, I wish that the radio cues for altitude matched your instruments. It's GREAT that aircraft with metric instrumentation use metric, while aircraft with Imperial units use that system. Too bad the audio cues are all in metric (which the resulting confusing is exactly the reason HTC standardized measurements to Imperial for all planes).
Assigning stick axes is awkward (honestly, why should you be able to MAP an axis inverted, rather than map an axis and then have a separate check box to reverse it which is 1000x's more intuitive?) and I always feel like some of my analog controls over-compensate. I've given up on trying to set my RPMs for cruise. Even with the axis fully calibrated and working normally,adjusting it even a little bit causes my RPMs to fall like a rock.
That's not to say it's all bad. Even without mods Il-2 is gorgeous. The aircraft modeling is beautiful, and there's nothing more breathtaking than soaring 15,000ft over the South Pacific with a CAVU sky. I like the added complexity of the engine management (set supercharger, fuel mixture, magnetos, etc) and the more robust damage modeling (although sometimes it seems a bit flaky how aircraft respond to damage). I like that in planes like the F4F you need to literally crank your gear up and down. Oh, and do NOT suddenly slam your throttle to firewall in the Corsair at low altitude if you're stalling out on landing approach (although beyond that, the Corsair flies almost exactly as she does in AH2, which makes me very happy. Just add in the more difficult gunnery and "slippery" controls. As Gavagai said, in Il-2 your nose is a LOT less stable than in AH. Much slewing around with even a little control input).
I'd play it more often if I just wanted a quick fix, but the game has a nasty tendency of crashing on me after playing for a bit.