I said this on Reddit but I'll say it again here:
If Apple wanted to, or intended to, read your iMessages, why wouldn't they design a protocol that specifically allows for this in the first place?
Finding flaws in a protocol which was obviously designed to be secure and then pointing the finger and saying "See? It's all on purpose" is just crazy.
But the masses will disregard the line right at the top of this article:
I certainly trust iMessage way, way more than I trust, for example, Skype, or even plain old SMS.
A much bigger problem is that iCloud backups are not stored encrypted. If you backup your messages to iCloud, Apple has no need to go to the trouble of intercepting your messages in transit.