Pros
What I love about Twitter is that everyone working at Twitter believes in the power of Twitter and the vision of the company. Twitter is making an impact on the world - and the employees are motivated to work hard to help the company grow. The work is interesting and constantly changing. The culture is vibrant and always full of excitement. There is a sense of community here that is unlike any other company - very supportive. Also, fun Friday happy hours! Breakfast, lunch, and dinner is provided - and the food is incredible. My personal favorite is the new smoothie/juice bar. You can work off the extra calories at the cross fit gym or yoga studio, or the SF fitness right by the office.
Cons
The company is continuously growing, so it's easy to start to feel like it's difficult to stand out here. It's on you to branch out to meet people outside your team.