UPDATE: It ended not being the brand necessarily. I used a CD drive cleaner and all seems fixed: http://joelmarcey.com/2009/01/05/macbook-pro-superdrive-burn-problems-update-fixed-with-laser-lens-cleaner/ This weekend I went to the Apple Store Genius Bar to see if they could find a resolution to my slot drive problems.
Well, it was the CD-R brand after all! I showed the Genius Bar representative my problems with my Sony (Brand A - I don't need to protect the innocent anymore) and my Memorex (Brand B) CD-Rs. She popped in a Staples brand CD-R (Yes, a Staples Brand!!!), and it burnt an iTunes playlist flawlessly.
Thus it seems the MacBook Pro slot drive is finicky; but better than having it sent in for repairs. ;-)
I am heading to Staples soon. :-)