TMP set the standard and sound for all subsequent Trek films. I love the main theme. It's probably one of my favorite movie themes of all time, and in many ways I like it much more than the Star Wars theme. Though that too is a great theme, I like the nobility and romance that can be found in the MP theme.
I really do hope that Michael Giachhino (sp?) reuses Goldsmith's theme in some way for the upcoming Trek movie. When we first see the Enterprise in NEM and the theme music plays, it's just an absolutely beautiful, magical moment. I really would like that theme to be used again.