Pros
Work life balance, company culture, company mission, benefits, people. Addgene is by far the best place I've ever worked. The mission is simple: make science easier for scientists. Because Addgene is a non-profit it cuts through a ton of crap that you otherwise might encounter trying to execute on that mission and still be beholden to investors. If you're on the fence about trying to work here: come work here. For my fellow developers: I'd say about half of the things I work on are fairly typical things (online store), with the other half being highly specialized (and interesting) software for managing / tracking / improving the growth of biological materials.
Cons
There really isn't too much worth noting, when I first applied to Addgene I noticed there weren't any glassdoor reviews which is almost always a good sign. Having worked there for a while now I really have nothing but good things to say. For the sake of completeness though: maybe the bathrooms could be a little nicer?