Pros
Despite staff often being junior, they're selected in such a way you have very talented and inspiring peers to work with. Fathom's activity within the local design, technology, fashion, culinary, and other bohemian cultures is relatively unmatched. You'll gain invaluable exposure and contacts. The culture is very family-like and contemporary. Aside from the gallery/event space, employees grow their own fruits and vegetables on the rooftop patio, cook/grill meals together, mix cocktails for happy hour, have dogs on-site, have access to a small handful of parking spots, wear pretty much anything within reason, go on field trips, etc. The lack of real job titles is a good and a bad thing. In the market it is great because you can be exposed to multiple agency functions and find your place in the creative world—designing, developing, in project management, leadership, vendor management, and more. On the flip side, you won't be compensated for the extra hats you take on. Leadership is very personable and the environment is very celebratory of diversity in race, gender, sexuality, etc. The smaller team with a sink-or-swim project training helps you to be self-sufficient and efficient (skills lacking at other agencies), so I'd list it as a positive if you are a natural problem-solver. You have a lot of chances to excel at your own speed, with very little decision-maker bottlenecking.
Cons
The work-life balance is the primary complaint and causes burnout. It is a consuming job that is suited for young, single, professionals with a lot of ideas and energy. If you're trying to settle down, this will be a bad fit. Compensation is the second complaint, symptomatic of the first. The pay is reasonable, but not competitive for the amount of work being done. Junior staff is happy with the pay, until their skills become senior. Lack of advancement on paper pushes people toward their next agency. Despite the semi-regular overtime project pushes, there is often little reciprocation because the small business regularly leans on its tight budgets and hourly quotas as the reason it can't promote. Benefits aren't that competitive. There is no partnership track, no retirement matching, no life or disability insurance, or anything that is common in places that strive to keep employees for 10+ years. If you require a support system of peers with like-skills that are senior to yours to mentor under, you won't find it. This job requires you to be a self-learner and will give you all the chances you need to grow on your own (both a pro and a con).