While I enjoyed the series in my youth. Vash is just another Anime stock character. The kind of character who goes from place to place changing the mindsets of others while following a set of "must only do the right thing" morals while everyone else in the world he lives in thinks he is a fool at first meeting only to later have gained something morally or some form of infspiration from his lifestyle. One of the most notiable aspect of this kind of character is his unablity to ever give up on his beliefs or set of morals no matter what the cost.
Other examples of Anime (that I have seen) that includes this kind of stock character include: Naruto, Bleach,...hell I can't name more because I haven't watched enough to really come up with a list. But yeah. I think you get my point.
Cobellanez
I watched Trigun all in one sitting. I really enjoyed it as well.