On a cold sart, my truck runs up to 1500rpms and will stay there for about 30seconds or so. it very slowly idles itself down unless i decide to throw it into gear. Then it idles down instantly and if i were to throw it back into park, the idle stays at the low idle stage and does not go back up.
If the coolant temp is below a certain threshold, it will start up with a high idle.
Your suppose to let any vehicle idle for atleast a minute before driving away anyways...
All 06-08's are programmed the same. I have an '08. Your truck is perfectly normal.

 

Most newer vehicles do this for emissions reasons, though you still benefit from warming the oil up faster as well. The faster the O2's and cats warm up, the less pollutants make it out the tail pipe.

I try to let the engine idle after cold start up (even in the summer) just to give the oil a chance to warm up. Start it up, put the seat belt on, fiddle with the radio, make sure my coffee won' t spill, put on sunglasses, etc.. after about a minute I drive off, but take it easy for a couple of miles until it's closer to operating temp. I don't hot rod it, or even tow anything until the oil has had a chance to heat up. Oil is designed to have the best pumping and wear characteristics at operating temperature. Anything less, and you increase the wear on the engine.

The couple of time's I've towed a 7000 lb trailer with 4 people in the cab, I plug in the Super Chips tuner, let it idle, and monitor the water temp until it's close to 200F before taking off. On a cold start, the oil temp is probably trailing the water temp, but it's better than just jumping in and taking off immediately after start up.