GameRager: Lol keep trying. Some are hella easy(God of War has alot but some you just have to tap the button alot and it will always work, while some is down to random buttons appearing onscreen.), and some are just plain difficult(Severances weapon combos for example).
For me I find it's how one holds the controller that determines if it's easy or not to do the combos right. I usually keep my right hand loosely gripped on the controller to allow the thumb to be able to hit the QTE buttons easier. :\
elisstar: For me, unfortunately it's a medical issue. The nerves (and thus my reflexes) are completely screwed in my right hand. For some games it's not a problem, but for others, like Indigo Prophecy, the game became unplayable at a early point. Such a shame, too, because I was really getting into it until trying that office QTE 1,000,000 times and finally quit before I put my fist through my monitor in frustration.
Anyway, that's why I like turn based combat so much!