It's interesting how most people joining toastmaster think the ultimate benefit of Toastmasters is the ability to speak well in front of a crowd. Even most toastmasters below advanced feel the same way. I have a totally different opinion. While we do become better speakers, I believe the ultimately benefit of toastmasters is it teaches us to think better.
Years ago when one of the best toastmasters I know told me this it just confused me. "What's this man talking about!" was what ran through my mind. Then I started to observe the various speakers while considering his comment. Indeed he was right. While a toastmaster has to get past the basics of communicating in front of a crowd (speak clearly, display no nervousness, use enhancing gestures, etc.), it's those that learn to really think while on their feet that are the best and most entertaining speakers.
Being able to think clearly is what allows one to prepare the best speech. Those who think quickly are the best table topics speakers. (Don't worry, if you're not thinking quickly and clearly at table topics or viewpoint rebuttals it's only a matter of time and practice before you are!) No matter how well presented its the thoughts that truly matter. Whomever said "its not what you say but how you say it" assumed a pretty shallow audience. Sure, saying nothing well will appear to be a reasonably good speech. Saying something well AND intelligent will have a much deeper and lasting effect on the audience. This is what Toastmasters ultimately teaches us to do.
Stick to doing regular speeches, taking on roles, and jumping up for impromptu speaking opportunities. While you become a better and more comfortable speaker, you will find yourself a better thinker as well.