I've had my first initial and middle name on my ID for 18 years and have only run into one minor issue at Dubai. Otherwise, it hasn't been an problem.
BTW, to get your ID to show your middle name, I was told you have to temporarily change your first name on the green screen to your first name initial, a blank space, and your middle name; i.e., (T. Middle). And I believe, you then leave your middle initial blank - not sure on that one.