Absolutely jdavis! I have been keeping them for around 15 years and have several 'Pilot' pens that light up so I don't wake hubby up. Often when I wake up, even after all these years of journalling, I think that what I dreamt couldn't possibly mean anything, but I still write it down and more often than not it does apply to my 'waking' life!
I find it great to go back through and see how I have grown in understanding what my dreams are actually saying, and even more interesting when they come to pass as many I have are prophetic.
I even used to type up all my dreams from the diaries and catalogue them, but as I am a prolific dreamer I mainly just type up the ones that I feel are important as there are way too many diaries to wade through now!
I have found that as I have grown and matured emotionally and spiritually lucid dreaming has become easier and I can deal to any unwanted intrusions in my dreams (usually ;))
There are definitely patterns, but then a symbol will be turned on it's head when taken in context with the whole dream and mean something entirely different.
Ha ha long winded way of saying it, but dreams are my passion. Well worth keeping a diary as there is much treasure to be discovered in dreams for you and others!