Pros
People - The people I work with are awesome! No joke - I love working with 100% of the people. They are passionate, humble, intelligent, and deeply knowledgeable in their domain. I've never been at a company where the people are this good! I believe there are several key things make this environment so great: 1) Upper management fosters the culture by example, 2) There are frequent, very small, check-ins to help people provide and receive feedback, and 3) the hiring process is "humane" - you don't feel like another number or an idiot-for-not-knowing-the-answer-to-problem-x during the interview process. Don't get me wrong - the interview process is tough - you are just not made to feel ridiculously inept after the interview
Purpose - The purpose of company (a Public Benefit Corporation) to enable teachers, schools, parents and students to make education better with data is a great purpose and gives you the "warm fuzzies" when you solve tough problems for customers
Product - The product meets the needs of its users in the way the users need the product. Having a very user focused product makes the product attractive and being close to the customer is very validating when we can solve problems for that customer.
Cons
As with any startup or smallish company, documentation is lacking and "tribal knowledge" abounds. Breaking through both of these issues is a challenge.