Great place to work, but is a growing company.
Pros
Personal Growth - it's still very easy to work on a wide range of problems at Pinterest. You can easily transition between different technologies and learn a lot. Impact on Projects - As a product engineer, you're able to have a lot of say in how the product changes and grows. Each product team is made up of ~10 people and owns a large portion of the product. Engineers are heavily involved in prioritizing projects for the team, and are involved from the beginning with the design and implementation of projects. Growth - the company is growing really quickly. There are plenty of negatives to that, but overall it's a great sign for the outlook of the company. It also leads to more opportunities to rise quickly in the company and to be a leader.
Cons
The main cons are problems that are standard with a growing company. As the company grows, there is some churn with employees at all levels. I've been seeing this the most on the PM side, as politics from the growth and resulting structural changes pushes people out. On the product side there's not a strong vision. It's very hard to get features removed and you have to jump through hoops to build anything new.