Pros
It is hard to give an honest review of this company without sounding like a shill, but my time here has been very positive. The team is small (10-20) people, and everyone has a great background for their role. The work environment is very casual and self-directed, and we often break out into group discussions about news or random funny events, which keeps work from getting monotonous (you could focus in with headphones on, if that's your thing). The office is in the Mission District in a diverse neighborhood, and I very much appreciate the quieter surroundings when compared to my friends who work in SOMA, and the easiness of a bike commute if you live in the city. The office is a large space shared with three other (non-tech) companies, and we have access to their industrial machinery space, a CNC machine, 3d printers, and a basketball space out back for breaks. Schedule is relaxed, and is work from home every Thursday. We are working on interesting technical/logistical/business problems, and we have found a very promising niche, which we are rapidly exploring with our new Series A funds. We are combining new developments in sensor hardware and machine learning/optimization, which keeps things interesting compared to optimizing ad clicks or search results. The CTO is a computational mathematics PhD, and it is great to learn from his extensive knowledge, which he is always ready to share and discuss. Because we are still small, every person has opportunity to be self directed and hugely impact the company. This in conjunction with a generous work life balance (rare in SF, but everyone here values their personal life) is why I am so satisfied with my job, and this company.
Cons
You could get a higher salary at Facebook/Google etc, few free lunches, basically only cons are related to compensation since I (clearly) am happy with the work experience.