Pros
Fun product if playing/enjoying music is already a big part of your life. You'll get to work with people who are legitimately passionate about music.
Cons
Accept a role here if you must, but be wary. I worked at the company for several years and witnessed many loyal and high-performing employees get laid off. At best, these layoffs were the result of real market forces affecting the magazine publishing industry. Notably, the business owner's adult children are (or were) both employed by the company and considered by some to be immune to criticism or feedback.
I ultimately felt there was little monetary or spiritual upside to my time at String Letter. In the event that you are laid off, it will likely be without severance (based on my experience and others I've known whose time had come) and with a skill set that may be considered outdated or out of step with the greater Bay Area economy.