I never let my car warm up, don't care if it's 20 bellow, I start it, I take it easy for the first few miles, then it's warmed up. I have a one hour commute, the engine will be operating in operating temperature for much of it...my street is a half mile long...I barely let the engine go over 1,200 rpm's while driving down it - I figure that's what the engine would be doing in my driveway - why not just gently drive it, not push it and get going? I'm not into wasting fuel or beating on my cars.
But yeah I know people that let their vehicles idle in their driveways for 5-10 minutes, just burning that fuel...then they wonder why they are getting 5 mpg' less than me. It just isn't necessary in my opinion.