Pros
This position was a great way to learn the ins and outs of the non-profit world - for instance, establishing and maintaining contacts with community partners, writing grants and assessing/meeting needs within the community. I was able to hone skills that I had learned in college and learn a bunch of new ones as well.
Cons
This is technically a volunteer position. While there is a living stipend, you will only be able to use it for just that - living. No matter how well you budget, there won't be enough to go to the movies, eat out with friends, go shopping, etc. In many ways this is a great aspect of the program, but it's worth it to seriously consider how you will feel working alongside (non Vista) co-workers who are doing the same job as you, but who are making 3 to 4 times as much. This is not a true "con" but it should definitely be a consideration. Before taking the job, be honest with yourself. And if you've already taken the job and think you want to back out because of money (or the lack of it) don't. It's only a year, and you'll feel pretty accomplished once you're done!