The aspect of this thread that I find hardest to understand is the decision to allocate the poorly equipped versions to transcon and other relatively long domestic routes. I recently flew BOS-SFO (a 6½ hour route with high proportions of "over-entitled" passengers, and mostly served in the recent past by 752s and A320s) in a 738 with neither E+ or any AV, when my understanding is that the great majority of 738s have now been fitted for E+.

Within the last month I also flew a one-year old 739 IAH-BOS, again with no E+ or AV.

I thought these types of equipment allocation decisions reflected either the relative unimportance of BOS in the network, or part of the airline's plan to discipline the over-entitled. It seems from this thread that the issue is more pervasive, however. I suspect the domestic equipment dispatching algorithms are looking at capacity only, taking no account of any other service characteristics.