Pros
Your coworkers are smart, talented, and engaged. The company is small; culture is actively managed. Benefits are many and well thought out - great health coverage, commuter benefits, stock options, free lunch 4x week, regular events and outings. Location is great - lots to do in the neighborhood. The problems you're solving for are new and challenging. There's a lot of freedom for experimentation and plenty of room to grow. The young market is growing.
Cons
The company skews young and it shows. Euclid is many people's first or second startup, or job. Young management makes some rookie moves. The big personalities (decision makers) listen best to other big personalities. There is a cultural schism - one side comes from finance and works like it, the other side comes from tech and works like it. The difference leads to trust issues, communication breakdowns across teams, and turnover in some (many) cases. Clear strategy and appropriate goaling would make a huge difference. Not really a con, but the market for the space is changing rapidly. Euclid changes to adapt, but not everyone is on board or even sees why. The real downside is the company suffers from a lack of a clear vision; no one is moving in the same direction in the first place, and when the company needs to change direction, it's harder than it needs to be.