I've been puzzling over this for a month or two.
Here's where I am on this, but would love to hear other people's views.
I've got a 2-7X30ish Hawke scope with 4 Mil dots on the HHA Optimizer Speed Dial.
UNDER 40 YARDS
Scope set to 4X and speed-dial to 20 yards. Parallax correction on the objective lens set to 30 yards.
With the scope set on 4X and zero'd for 20 yards, Mil-dot 1 is good for 30 yards and Mil-dot 2 is good for 40 yards.
Sooooo.... my strategy here is that if I've got deer walking in and they are going to be inside 40 yards I'll probably leave the Speed Dial set at 20 yards, the scope at 4X, and gap-shoot the dots. Things change quickly inside 40 yards and you don't always get second chances. Fiddling with a range-finder and speed dial with deer close by could get you busted. I usually range the trees around my stand at the beginning of my hunt so I don't get caught ranging deer when they're close by.
Anything out beyond 40 yards will likely require more time and magnification to pull off a good shot.
OVER 40 YARDS
At longer ranges you've generally got more time, and there's less chance you'll get busted fiddling around with range-finders, speed-dials, and such. Also, it gets pretty impractical to pre-range every tree in the forest out to 80 yards or more.
Sooooo.... for shots over 40 yards I'm thinking:
Range the critter, or where they are expected to walk.
Turn the scope up to 7X and set the Speed Dial to the correct range. Set scope objective to correct range.
Take the shot and when you hear the deer crash select the BBQ sauce of your choice.
Remember to set your speed dial back to 20 yards, scope to 4X, and parallax correction to 30 yards.