Pros
Twitter is an amazing company, the culture is very respective of everyone's personality and opinion. It is a very open environment and anyone can come up with ideas or projects.
Cons
Even though the culture is open and the limit seems to be the sky, Twitter has strong limitations due to its very limited resources. The approach to risk is also overcautious. But nobody says "no" at Twitter, there are always ways to be creative and do things! Another cons is with respect to management. The hiring process is quite dysfunctional and we are struggling to attract great managers. Growth is limited. Don't expect to have your career at Twitter. It's great to spend 2-3 years there and learn as much as you can before moving to another opportunity. The management will do what they can to keep great performers but the opportunities are quite limited due to restricted resources.