I love the Wall Street Journal, and I particularly enjoy it's Arts and Entertainment section. Here is a wonderful article called "In Praise of Infidelity," which explores the question of staying true to the score in musical interpretation.
Sometimes I feel compelled to put more expressive markings in my own arrangements--that I should give some extra guidance to the musicians as to how to phrase a particular passage, or what tempo to choose, or what dynamic to play. On the other hand, I find it frustrating, because I rarely can decide from one moment to the next how exactly it should be played. Plus, I rather enjoy the idea of letting someone give their own interpretation of the notes on the page.
After reading the article, I think I will continue to be sparse in my directions--as Bach was--and allow the musician to come to his own conclusions. (And yes, I am laughing that I just compared myself to Bach!)