Music Theory - Should Musicians Bother Learning It?

Plenty of people can make some music with an instrument, but that does not mean they know what they are really doing.  Everyone wants to play songs, but who wants to take the time to learn the music theory behind what they are playing?  Music theory is complicated and it will drive you nuts, but those hoping to become true musicians will learn it.  It will make a musician.
In my last post I discussed my venture into the world of learning guitar.  When I decided to take guitar lessons I  got rid of the notion that I could merely strum strings and move my fingers to be a great musician.  I realized I'd have to strum and move my mind as well.
Now, I came in to guitar lessons with a basic knowledge of theory.  I have been a music lover since childhood, so I was aware of staffs, notes, rests, time signatures, beats, measures, and what these all should mean to me.  Just knowing this has proven to help me become a better musician.  When I came into lessons, I was able to tackle more in a short amount of time simply because I knew how to read music.
Despite understanding that I was better for knowing this basic theory, I still did not imagine I would have to learn theory in-depth.  I was wrong.  In my last lesson I was presented with a chart known as the Cycle of Fourths to memorize.  The Cycle of Fourths is a chart representing the relationships between the twelve tones of the chromatic scale and their key signatures.  It sounds difficult because it is difficult.
One wonders why I would bother learning this frightening Cycle of Fourths.  I'm bothering because in the short amount of time I have begun memorizing it, I have already seen growth in my skill.  Patterns in music that were a mystery to me before are becoming clear.  Not only can I make music, but I can understand how I am making that music.  It is an inspiring feeling.  I have gone from feeling like someone who can make music to a musician.
So I would suggest to anyone with the desire to be a musician that they take the time to learn music theory.  It is difficult and frustrating learning the language of music, yes, but it is well worth it.  If you want to live the dream, you have to understand it first.

For fun and interactive lessons in music theory on the web, I suggest Ricci Adams' site.