Amazon

Lots of opportunities and challenges of scale.

Rich problem set to pick from.

Lots of existing skills and specializations to tap into for collaboration on impactful projects.

Excellent set of engineers in the wider organization, and a great team of colleagues.

Amazon's "values" and culture are really well-explained; employees follow these tenets, and you can clearly see why a large company is able to work efficiently and nimbly as a result of this culture.

For someone from a smaller shop, the large organization may be overwhelming and sometimes confusing. However, colleagues are always there to help point you in the right direction when you need to.

Large company-wide initiatives are possible, but you need to be patient and plan them right.

Protect your time -- there's a lot of interesting stuff happening at the company; prioritization of what you want to work on and protecting your time from meetings cannot be overemphasized.

Amazon culture is a huge part of the success of the company, as I see it. We should strive to maintain it, and grow and evolve it with the company and the times.