i guess cheating is when you make something possible, when the musician involved cannot do it. i.e.
-using auto tune on a singer who can get the part right but is pressed for time = not cheating
-turning a 100 bpm guitar solo into a 220 bpm cause the guitar player cannot play that fast = cheating
there are also cases where you make things obviously impossible, which is not cheating. i.e.
-trigerring 2 kinds of snare sound on a drum beat, or impossible ostinatos that can only be done if you had 4 arms.
i guess thats my point of view. sometimes you just dont have the time to get something right, so you do some shortcuts. as long as you can do it live, it is all fair