I just got a brand new TL and have about 200 miles on it. I'm so eager to punch it, but how bad is it for the car? I've heard some people say it's better to work your car hard when you first get it.

Waiting until i hit 1500 miles to gun my TL out of the question?

 

Check the 3G garage thread; this should be addressed in there. I believe the break-in period is 600 miles. If you need to drive for an extended period on the highway before then, make sure you vary the revs (for example, shift down to 5th for 10 to 15 miles, then go back to 6th).