Pros
Some great colleagues, nice office space, flexible working hours, plenty of food and snacks (although the former is much reduced and declining in quality), good benefits (health insurance coverage is excellent).
Cons
Where to begin? Twitter has a huge management problem. Every team is in its own silo, thus creating a lack of internal coordination about efforts that is palpable when you find yourself duplicating work someone else is already doing. Managers encourage this 'silo mentality'. Priorities change and are defunded overnight, despite all the work and cost. I've seen many colleagues' projects being finished after a year, even when they are close to completion. It seems to me like middle and upper management discuss these things for months but don't tell anyone (talk about transparency). Then, one day they will announce it and expect you to move on. It wouldn't be unusual for them to schedule an off-site around this time as an opportunity for you to show you're on board. Get drunk, smile and carry on. People who have received promotions are definitely not qualified to get them, but they do whatever they are told and that's enough to get you one. It's insane: I've seen people change jobs internally two and three times a year just because their VP trusts them and nobody else. Lastly, there is no product vision. When big projects fail, they don't acknowledge it.