How do you use it to login to captive WiFi portals?
In rare cases where broadcast is required or even more diabolical network asshattery is afoot, I create a bridge on the Mango Lan<->Wifi with brctl. Of course, then your laptops ethernet MAC is exposed to the Wifi on the other side of your Mango. Even then, I've got a pretty snazzy etables filter to keep that hot mess under control.
Did I have any trouble at all with pandora on my phone or netflix on my ipad while I was in Europe or Australia? Nope. Never even gave it a second thought.