Yep.

I have heard very good arguments from both sides of the fence. The way I look at it is this:

Whenever you get a new rifle/barrel, you are going to have to find what it likes best with regards to ammo. So in effect, when you are playing with your new toy, and developing a load for it, or even finding a factory load it likes the best, you are, in effect, going through the "break in" process. Does it hurt the gun? Probably not much... Does it help the gun? Probably not much... But it does help you become accustomed to it again, and find the ammunition it shoots the best with. Everybody wins.