I regularly fly with Virgin Atlantic, and their new 787s have a fantastic wifi service courtesy of T-Mobile. I worked a problem during a recent flight from London to DC spending the entire flight remotely logged-in to remote applications over Citrix XenApp. Latency was poor (you cannae change the laws of physics) but consistent and throughput was perfectly fine.
The cost? £15 for unlimited data for whole the flight. Even better, on my second trip I discovered the service is included in my monthly iPass Mobile Connect subscription, so my incremental cost was zero!
I understand they're using ka-band satellites with approximately 70Mbps per channel. I guess they can always run multiple links if usage takes-off.