Pros
Great technologies, the smart engineers Twitter hired from Google etc. between 2012 and 2013 made a lot of difference to the in-house tech stack. A lot can be learned from what still is available there Decent tools and IT department, though engineers complain about them. Twitter has a surprisingly mature internal tool stack as compared to other companies and many people realize this after they leave.
Cons
Management is overly political, which shows that they are not good at anything. Especially higher management (Sr Directors, some VPs), who have fired people they did not like, hired and kept favorite people around and have made this very obvious to the entire organization. If they were any good, at least they would do this without making it very obvious. Senior leadership rose to that level within 12-18 months and since they have no idea how to scale gracefully, they fail. Just hoping that some of the political people Sr Directors/VPs left behind are fired soon so that Twitter can be saved.