I was recently in the USA for business and due to the past experience with BA’s delays (3 trips to San Diego in 2012), lack of comfort on the economy cabin of the 777 from London and significantly better price I’ve changed habit and went for Delta with connection in ATL when going to the US and in JFK when coming back.

Web checking was problematic in both direction: it wasn’t possible to book the seat for the domestic flight and I had to check-in at the airport and get the actual seat at the gate.
This was nicely compensated by the fact that both times I was assigned a seat in the comfort economy and I was able to sleep fairly well.

The in-flight entertainment was a bit problematic in both intercontinental flights: audio was missing in my seat row (not only my seat) on the flight to ATL (overhead monitors) while in the flight from JFK the system had to be hard reset to deal with major problems in playback (individual screens, system running on RedHat Linux dating from the 2002-2003 period) and the resistive touch control on the screen was not working in the lower left part.

I think that in the future cabin refreshes all that will be needed from the entertainment point of view is power outlets (CA and USB) and a simple retain system for the tablets that are becoming more and more ubiquitous.
If differentiation is desired an app (android and iOS) to stream content from the USB link should complete the needed package.

The quality of the seats, or to be more precise the fit of the seats to my body, were more than compensating the issue with the entertainment system.
The overall balance was good: Delta will be high in my preference list for future trips to SAN.