A little update. Today I hooked up my wifey's iPad on the 5GHz channel and it too worked flawlessly, except for a couple of short millisecond "blips" now and then (2 in 30 - 45 minutes), which I can definitely live with. I believe if I move the AE into the cabin, it will work without interruptions.
The audio quality from Spotify is simply amazing. I cannot tell a difference between it and CD with the Mobridge pre-amp, after doing an A/B comparison using my reference CD brothers in arms by Dire Straits.
Another cool thing I found out is that you can jailbreak the iPhone and set-up a wifi and BT hotspot without any additional costs. So yesterday for example my daughter was in the backseat with my macbook and she was connected to the internet on a 6 hour trip via BT and my iPhone's 4G data connection. It worked great.
What you can also do with the hotspot is to use an iPad or iPad mini to play the music instead of the iPhone. The data will stream from the iPhone to the iPad via BT, and then to the AE via wifi. Works great, but I have had some delays when the music setting is on "extreme". It seems the BT connection speed is not always constant.
I'm so excited, putting all this awesome technology to good use!
So now I will probably upgrade to an iPhone 5 or I will get an iPad mini.