I think sites like Netflix and HBO Go are blocked, aren't they. Look at the FAQ that UA points you to on the GO-Go site.

Q:Why can't I use Netflix, Amazon Prime, HBO Go or other streaming video websites?

A:Bandwidth at 30,000+ feet is inherently limited, and heavy-load activities like streaming videos from the ground can weigh down our network. That means playback is subject to poor video quality, buffering, and slower connection speeds for your fellow passengers.

Gogo's Wireless Entertainment service, available on select airlines and flights, is optimized for delivery to your device from a server housed right on the plane. This server can hold 100+ titles which are updated frequently, so there are always new and intriguing selections ready to enjoy. Plus, you won't have to pay for an Internet connection!