This was the number 1 reason I switched from UA to AS for transcons. Ran into a 1K I used to do business with, and he just switched to VX for the same reason. Once you start using it, you get used to it, and I can't imagine a 5 hour daytime flight with no connectivity now.
UA and B6 are the only transcons now out of the DC area without Wi-Fi, and B6 has just 1-2 west coast flights a day from here. DL, US, AA, AS, even 1/2 the WN flights out of BWI have it. This isn't channel 9 or seat back IFE, this is a business service, and without it, UA's in-flight service is becoming as dated as it's 757s.