It's relieving to hear that the TB one is technically superior, but I don't see how it is intended for the MBPr - it is a checkbox in the Apple's MBA order form as well, along with all the other TB adapters which are mutually exclusive.

And even if the USB adapter is dog-slow, it's all I'd need onsite with clients (email, Skype chat). I'm still not sure if I made the right choice in the long term :/