I've done quite a few S/E taxi outs on the 777... Well, shut one down when confronted with a long delay and a need to keep moving. Unfortunately, our manuals have been changed (Boeing?) to forbid S/E taxi above MLW, I guess due to jet blast.
Came out of JFK last year on a Sunday morning. Asked ATC if there were any delays: "No". Taxied round the corner to find about 60 aircraft in front; nearly two hours later got to take off. If we hadn't shut down one we'd have been back for more fuel and another long wait...
I don't have a problem with starting an engine a few minutes before launch - if it doesn't want to go then I don't particularly want to fly with it anyway!