Progressive lenses?

I had an eye examination a couple of days ago.  It seems that I should now consider getting progressive lenses (or separate glasses for reading, etc.).  The gradation shown on the prescription isn't large, but the optometrist said that it's best to start with progressive lenses early, so as to "train the brain" to handle the effects while they're mild.

I'm not keen on the idea, frankly.  Part of my reluctance is that I don't think I fully understand what this "training" involves.  Am I correct in thinking that if I were wearing progressive lenses and tilted my head up and down while focusing on an object, I'd see the image distorting as my line of sight with the object passed through the gradation?  I think I'd find that very distracting, at best.