Vantaggi
Depending on your job and the project, you may get to meet some incredible people and get to attend the occasional conference. Also, during my time there, my coworkers (but *not* upper management) were great. That said, turnover is so high, most of the staff has changed already.
Svantaggi
Upper management have no real long term strategy. The answer to "what are EDN's 5-year goals" is different every day of the week. EDN's mission statement to "expand and broaden the environmental movement" does not guide its strategy or policies in any real way. In fact, the mission statement should just read "to keep EDN afloat." When it comes to funders and partners, EDN's motto seems to be "overpromise and underdeliver." Time and again, upper management will promise something impossible to a partner organization, will not be able to deliver on that promise, and will lose that partner or funder forever. Very few serious organizations still want to work with EDN. Next, you can work 70 hour weeks and upper management will still think you're lazy. Two of my colleagues pulled together an incredible event, an almost impossible feat, and they got no credit and no thank you. At the same time, when upper management's 'out of the box' ideas inevitably backfire, some poor staffer (whoever is on their naughty list that week) gets blamed for it. That's why staff turnover is the highest of any organization I've ever seen. Of the people who were there for Earth Day 2014, only one stayed for 2015. Of all the staff of Earth Day 2015, only two stayed till Earth Day 2016. As it's looking now, no 2016 staff will be there in 2017. Upper management is in the office a few hours a week at most, and spends most of that time distracting the staff, demeaning other (actually successful) environmental NGO's, and complaining about EDN's board. Sure, Earth Day 1970 was an incredible event, a wave that activated millions of people and birthed the modern environmental movement and inspired the clean air act, clean water act, and other laws. Earth Day Network in 2016 is an empty shell with no real ideology, no real following, and certainly no real visionary leadership.