I couldn't get Gogo to work at all on 2 of my 3 flights last week that had Gogo. I could use the onboard entertainment, but trying to buy a pass / use the T-Mobile option just got stuck. Tried two different iPhones.
The VIASAT flight worked great - $5 flat fee and got 20+ Mbps download speeds. No account creation required - just a one-time credit card purchase.
I have suffered through dozens of NY<-->LAX flights over the past several years, paid Gogo a couple of thousand dollars in fees, and won't miss them one bit when they are gone!