I was able to quit pushing mongo pretty much immediately once I found out it was frowned upon, but I totally disagree with the whole faster setup thing.
I pop off the tip of my tail, so it's really uncomfortable to setup my front foot with my back foot like that. I'm pushing, putting my back foot on the board (usually over the bolts), setting my front foot, then setting my back foot. Pushing mongo (which I don't actually do anymore) I can push, set my front foot, then set my back foot.
Never really thought about it much. Probably why I suck at quick set-ups. Are you guys setting your front foot with your back foot already 100% set in ollie position? I could do it, but it just doesn't feel right, especially for something like a heel flip or varial heel.