I am an Iron Maiden fan (who isn't) so I really found a little bit of errors in it. Not a whole lot, and I wont critique the voice, but there are some. The first one I caight was that it was a little slow.
Fine up to the "Let he who hath understanding..." part. That was supposed to be done at a faster pace than the rest. Besides that the speed was fine. Now another part I cannot explain. It just dosn't have that feel.
Maybe it's the lightning effects thats missing, but I dont know. Maybe it's that subtle echo that the voice has in the real song that's missing. Either way, something is. Next time do the whole song. Get it Acustic and start singing. NOW!