I used NationBuilder extensively from about 2010 to late 2014. I used it for several political campaigns, including a statewide California ballot measure. I also did some of the first extensive custom work and authored several front end hacks. I built a startup that consumed NationBuilder’s webhooks API. I’m a full stack web developer with a background in political campaigns.
Potential users of the platform should consider the quality and reliability of the company behind it. In my experience NationBuilder was incredibly unreliable. I would never again rely on it for anything at all. I had the platform break things like CSV exports in the middle of a live demo. In 2012 I was promised a voter file they never delivered, creating havoc for the campaign. In 2014 I had their API break several times, putting my clients in jeopardy of breaking campaign finance law. We nearly refused to support it, though that would have cost us money. Of the three political payment processing APIs we supported, we had no issues other than NationBuilder. And they broke their production API three times in as many months.
The staff turnover there is incredible. The only way I could get their API fixed was to talk to the engineers, and in 6 months about 3 of them came and went. Senior staff would make different promises to our organization depending on whom they spoke to. Check out their glassdoor.com reviews for some insight into the company, and ask yourself if you really want to depend on them. I did, and it was a massive mistake, the largest I’ve made in my career.