Pros
The people make it. There aren't too many teams, but the ones that are there are impactful running major company priorities. It has a small company vibe, and is generally a pleasure to go into the office each day. The product is great and all sections of the UK office from Sales, Media Partnerships, Engineering, are passionate about the company.
Cons
Working with San Francisco is a drag and can mean late nights at the office. The place can feel a bit disorganised too. The company grew quickly with the expectation that lots of stuff that was poorly designed/architected/written would be fixed as the company grew, but now isn't being focused on because there isn't the staff. This can seem surprising, but really is a bit of an opportunity - there is low hanging fruit all over the place and a chance to be impactful. There is something said of the company that one chooses "either the legacy system, or the system that hasn't been productionized used yet".