I would stay far, far away from Moz as long as Rand Fishkin remains the voice/face of the company. His influence breeds a culture of self-righteous, unprofessional, indignant people, and until you cut out the cancer, I don't see that ever changing. His response on Twitter when a paying client pointed out that it was unprofessional for Moz to send out a partisan company-wide email and share that email publicly was "Please feel free to unfollow. Only a click away!" He publicly smears people in the industry instead of going to them privately with his concerns, most recently putting Copyblogger on blast without reaching out to its founder with his feedback first.
When I worked there, 14 people quit and only two left for lifestyle reasons; the rest couldn't stand working there any more. I found it completely inappropriate that family members were on the company payroll despite their lack of experience or relevance to the industry. I witnessed numerous instances of sexism/favoritism but if anyone ever spoke out or complained, their career there was basically killed (either they were fired or promotions/upward mobility died and the employee ultimately left out of frustration). I worked with extremely talented, amazing, hard-working individuals in various positions, from entry to officer level, who all got screwed over because they provided pushback or constructive criticism that countered what Rand wanted.
If you're the type of person who likes to voice his opinion and is not afraid to offer up constructive criticism or disagree with someone's idea, or if you don't like being forced to dislike someone or burn bridges just to stay in the founder's good graces, this will not be a good environment for you.
A previous review mentioned the fact that Moz is a "12-year old VC-backed startup that has never been profitable." The reason is because the foundation is toxic, which seeps into leadership and company vision. I don't see this company's issues changing if its founder doesn't start acting more professional.
If you're the type of person who likes to voice her opinion and is not afraid to offer up constructive criticism or disagree with someone's idea, or if you don't agree with the notion that you have to dislike someone because your boss does (basically if you don't subscribe to being blindly loyal to a fault), this will not be a good environment for you.