I play AP Ezreal myself, I love him a lot. That said, about this guide... It's well written, and most info is correct in itself, but there's a few things I'd like you to point out, in order for an upvote.

1) Why is Ignite not an option on a AP Mid Carry? Most Mages use it, why should Ezreal stick with Teleport, Clarity or Heal? And as far as your statement goes: AP Ez hardly has troubles with getting outleveled - at least in MY experience. I've beaten LeBlancs with it, which is a rare sight to behold.
2) Why go for a Tear of the Goddess instead of going for... let's say, an instant Sheen into Lich Bane? You sacrifice a lot of early game power for something that doesn't pay off until relatively late in the game, at the expense of a lot of gold. Tell me.
3) Why the one point in Defense? |D Increased Neutral Buff Duration is way more useful than the 2MR you get from the point specced in Resistance .
4) Why take Mystic Shot at Lv.2? It's - as you said - least useful on AP Ez, and has next to no damage before a Sheen/ Lich Bane. Why pick it up so early over Arcane Shift?
5) Why no AP in runes? I've always found starting with 30~ AP to be one hell of a help, seeing as how high Ez's AP Ratios are. Why spec into full Magic Pen, while most enemies won't go over the 30~ MR?
6) You build no sustain (i.e. via Will of the Ancients or, which I like, Hextech Gunblade with Mystic Shot applying LifeSteal and all): What gives?

So yeah. I'd like to see your feedback. I like AP Ez, I like the guide, but just these few things. Also, Comment2Vote helps keep away the "AP Ez noob"-votes, unless they also comment it.

~Emo

Try working for the tears of the goddess after boots of speed, because Ezreal is very mana dependent, and try replacing flash with ignite, because with Arcane shift you can basically flash through walls ever 19/17/15/16/11 secs, other then that good build