Pros
The team is a delight to work with. The people here are not only extremely competent at what they do (teaching, design, business, engineering, etc...), but are also thoughtful, communicative and responsible - a pleasure to collaborate with.
Even though we are primarily a frontend (javascript) shop, we do get to solve diverse and interesting problems - from the theoretical, algorithm-heavy work of rendering equations and creating our own scripting language, to the design and human-centered problems of creating very specific pedagogical interactions.
The mission of the company is great, and it is the most beloved ed-tech company in the world (just search for desmos on Twitter). I regularly get stopped on the street when wearing my company shirt by math teachers who love our stuff.
The company culture is also fantastic! We have flexible schedules and I work from home once or twice a week, since my commute is around 45 minutes. Sleep and time off work is seriously valued by everyone, as many people who work here have families and kids.
Cons
I feel like I couldn't work anywhere else. I've been spoiled.
On a more serious note, we haven't done a great job of recruiting folks from more diverse backgrounds. This is something that everyone is aware of, and is something everyone at the company is working on improving.