An update on EZE.
I flew out on 12/27 on United. The airport was the usual chaos, long lines at check-in and at passport control.
The additional security was not as bad as I anticipated, I was traveling in C so I was one of the first to board. The flight left maybe 20 mins late and arrived on time in IAD.
I would guess that UA's flight being a 767 helps since it carries far fewer passengers than say AA's 777.