I'm flying from the east coast to LAS in a few months - not a route I usually fly. Though I am a loyal US traveler, I will likely look to UA for this trip because I would imagine I'll have trouble upgrading. If I don't get to upgrade on UA, I am certain that I will be in E+. That offers enough of a difference to tip the scales in favor of UA. This is the downside to pulling those F seats.
When the strategy came out to offer lower F fares, I thought this was a stroke of genius because it would justify keeping the large F section in the 757s and, if promoted properly, could generate new high-end business. Unfortunately, CCY seems to be working at crossed purposes here, announcing a limited program of reduced fares in F class while pulling the seats at the same time.