Numbering boarding makes you stand around in line in every rolling delay. I am not hot on that. Nor would I be cool connecting where any delay (caused by WN) causes me to not be able to get a good seat when I arrived for my flight.

It works for WN, but if you think for even a second about it, they reserve A 1-15 for Elites and people buying more expensive fares. So on a flight with 143 (-700) and 175 seats (-800) they have 15 elite/business travelers. On many UA (or DL or AA) flights actual elites/business travelers may be 30-50% of the passengers. WN just has a very different customer base which requires different solutions.

IMHO the UA effort to follow SW (with 5 different lanes) is silly. The real problem is that they gave "elite boarding" to everyone with a credit card, and trying to charge for it, and that combined with charging for baggage (so more people use roll-aways) causes a lot of folks who used to board with their group (see PM UA system) to crowd around to try to get on the plane.

I don't have much recent experience with AA, but flying DL or AS or VX I have not seen the same type of crazyness I see on UA.