Gogo In-flight WiFi evaluation
I bought in-flight internet for the first time several days ago, via Gogo Internet. It was a 3+ hour flight on a plane with DC outlets underneath the seat. Airlines have recently been offering in-flight wifi in the past year as a premium service. The technology for in-flight wifi is interesting–the plane actually connects to cellphone towers on the ground to beam data. I had always assumed that satellite technology would be more efficient, but I suppose that operating costs would be even higher.
Given that the connection is based on cellphone tower technology, one would assume standard 3g data rates. That is exactly the case:

Of course, data rates vary tremendously, depending on location and the number of connected users.
Overall, the data speeds were tolerable for email and basic web surfing.
In-flight Wifi starts at $8 per flight if connecting on a mobile device, and $12 upward for laptops. Frequent flyers can also purchase monthly passes. I’d recommend using Seatguru to find the best flight/seats that have power outlets. Be wary of advertised power outlets though; a recent AA flight I took on MD-80 equipment advertised power outlets, but they were in the form of cigarette lighter outlets!