Pros
I had good engineering chops before working here but AddThis is where I learned to apply them at scale. Your work literally impacts a billion users - walk in to any room and most of the people there will have AddThis javascript cached on their phones. I don't know of any other companies this small with so much reach. The company is the right size so you can still make a huge personal impact, rather than working in a farm of other engineers like at Google or Facebook. The people are nice too, I consider a lot of them to be friends.
Kontras
Pretty unstructured, they expect you to figure out a lot of your work on your own. I wish the lunches were healthier. The office can get pretty noisy too if you don't like headphones. We've gone through some turnover lately on the sales side, it was worrisome at first but the changes seem to be working.