Mark,
Six years is a long commitment. However, you can always resign if it's not your cup of tea, so you're not necessarily committed to the six years.
Pros: You are part of the decision process. If you didn't like the way the Association has been doing things, you will be in a position to affect the decisions to change how things are done.
Cons: If you do it right, it's more work then you think it is (and it's more than a monthly meeting).
You will get some thanks but mainly you will likely get complaints (that's part of being on the Board).
I have found that the more that is done that members can see (tree trimming, repairs, etc.) and the more information flows from the Board to the membership (newsletter, website, etc.) that you will get a lot more thank yous.
Here are some general resources that might help (once you have a specific job - officer position - there are more specific resources):
The Board Member Tool Kit: A GUIDE FOR COMMUNITY ASSOCIATION VOLUNTEER LEADER From CAI
DOs and DONβTs for new HOA board members article by a FL attorney
Advice for New Board Members: After Election, the Real Work Starts article from the New England Condominium magazine
Common Mistakes New HOA Board Members Make article from an insurance consulting company (good info)
Hope this helps.
You will likely enjoy the work once you settle into it.