Pros
It's hard to beat the cause - physical activity is really important and should be promoted more in our culture. Most of the people working there are from the sports/exercise world and are really passionate about the cause. Though it is a small team, ParticipACTION really employs hardworking people. In my time there, it was common to wear a lot of hats, not unlike a startup. I think it's a decent job early in your career, as you can learn many things.
Cons
Most of the people I knew didn't receive a competitive salary (regardless of their experience), but that is common in the non-profit space. While most of the leadership team was great, there were a couple of bad apples that strongly affected the dynamics of such a small office. I also think there needed to be more diverse hiring practices at that time.