Pay: Amazon doesn't pay especially well in terms of salary. They have "total compensation" which probably includes two years' of cash bonuses after your start date and a package of RSUs which really don't start vesting for two years. My "total compensation" was $10K higher than my salary, which isn't bad but leaves you at the mercy of the stock price. Advancement is slow; aside from a nominal COLA-like raise once a year after reviews, it can take a few years to get promoted a single level within the company, and even then the raise may not be that impressive. Basically what it comes down to is, your salary when you enter the company largely determines what your salary will be during your career there; they're mostly going to reward you with RSUs, not raises, which are really intended to keep you at the company longer.
Advancement: This is a complete mystery to everyone involved. Three-plus years and I never figured it out, except that it has to do mostly with your direct manager. They're responsible for representing you in the process, so a sleazy manager who promotes you heavily is good to have a review time, but a disinterested one or a bad communicator will basically leave you hanging. Sadly, in my experience, this is how advancement and reviews work at Amazon; they don't have much to do with the quality of the work at all.
Management: Management is totally mixed at Amazon; some are great, some are terrible (in my experience MBAs are let run amok, and seem primarily to promote one another, at least in my group--we had a bunch from the same school). Some people get micromanaged, some are left to their own devices. As a matter or practice, Amazon hates managing people--most managers have no more than three or four direct reports, so there's a lot of mixing things up on teams: senior employers get one employee stuck under them and that sort of thing. That's one of the main reasons the experience of management can be so mixed--there's so many people managers who may or may not actually be assigning you work that it becomes a matter of personality.
Environment: The workplace is weird at Amazon--it's aggressive for sure, but not exactly a boys' club, so that's a plus. It is a very accepting of diversity place to work. But overall, there's a lot of confusion. They're constantly shifting levels of management, and theoretically everyone "owns" a core set of tasks or products or whatever, and there are channels that are supposed to be used to communicate with other owners and teams ("up and over"); in practice, this rarely if ever works, and if you want to be successful you have to friendly, reliable, and willing to take on other tasks for other people and work constructively with others, because frequently employees simply get together to solve simple, short-term problems and completely circumvent management (who prefer to have lots of agenda-less meetings to deal with problems). In that sense, Amazon is an extremely political place to work, because you constant risk stepping on someone's toes, crossing an unseen boundary, or things like that. If you're not a communicator or not friendly, this may not be the place for you. It's also a company that's basically relentlessly positive--it's typically bad for you to "go negative." They don't like to blame individuals for problems; even big issues are typically dealt with with a meeting where all the stakeholders get together and divvy up blame so that no one's left with all the responsibility. In a lot of ways this is good, but by the same token people's unwillingness to risk seeming negative creates an environment where there's a lot of evasion and frequently an inability to hold poor performers accountable for their work, particularly if they're gifted at skewing metrics in their favor. Remember, it's a political place to work, and if you can't explain something to a manager in a Blackberry-friendly format, they simply do not care to learn.
Career Development: Aside from the fact you'll get great experience, learn a lot, and have a great thing to put on your resume, Amazon is a horrible company for career development. Lots of people leave after only a couple years. The weak pay scale means that you can get paid more with the experience you get there, while Amazon is largely incapable of communicating anything about career development that's useful. There's lots of talk about it at review time, but no follow through. There's virtually no internal career development opportunities, especially if you're not a developer. That said, it is a company that invites moving around internally. After one year, you're free to look for other positions in the company, and most employees are perfectly happy to sit down for lunch with you and discuss what goes into their job and what their team's looking for. So basically you have to network the rest of the company if you want to get anywhere, but be aware--changing jobs does not by any means equal pay raises or advancement.
