You will get all sorts of methods and reasons and theories for warming up or why not to warm up. With the crazy cold we've been having i let mine warm. The seats are freezing the windows are frozen, and i'm too cold to start driving and can't see anything out the windshield. It warms up while i scrape the windshield, or brush snow, choose a station and adjust my seat and warm up the steering wheel.
Here's my crazy technical reasoning. If idling 2 minutes doesn't hurt it, why not take the precaution.
More importantly though is probably to ease on out into the street and not race it out of your parking spot. That probably makes more of a difference since it is slowly working the rest of the drive train that isn't warming as you idle.