Pros
The company has a genuinely solid product portfolio and happy customers. The HR and Facilities teams make the office a nice place to be and will more than go out of their way to make you feel welcome and comfortable. The on-boarding process for new employees is better than anything I've experienced before. As an Engineer, the technologies are more often than not new and fun to work with, you're always learning and there is no shortage of interesting problems to solve.
Cons
There is a ton of bickering between the various teams at Twilio, and thinking about it as I write this, the level of spitefulness is higher than anything I've ever experienced previously. We love to talk about small empowered teams at Twilio, which we have and are. But, an unintended consequence of the myriad engineering teams at Twilio is the unproductive competitiveness. Teams (and colleagues) very frequently trash one another behind closed doors rather than practice empathy and collaboration. My take? The highest levels of Engineering management are quite adversarial and stand-offish. I don't interact with them often but in the few meetings where I'm exposed to them it's awkward. The fish rots from the head down, and I can't help but wonder if they're responsible for the conflicts and promoting some of the poor relationships found amongst the teams. Ultimately, you'll notice there is more thought on how to push engineers out than effectively growing existing ones.