If you really want to throw this out of kilter, let's add CO to the fray...They are the best when it comes to domestic F, followed closely by AA.

Regarding the UA 319's, they are getting an added row of F, to 112, to give them commonality with the 320's to make them more interchangeable.

When, I don't know--but it has been announced.

Where US falls short is no meals whatsoever on any flight under 3.5 hours in any market. Their food is generally inferior to competitors, but I haven't flown UA in a while to compare.