Work-life balance is non-existent. Amazon expects you to marry your job. If you're on salary, expect to work a minimum of 50 hour work weeks. During Peak, you can expect that to be a minimum of 60 hours. Taking time off will undoubtedly put you behind, requiring you to use the time you don't have to catch up.
Benefits are almost laughable for a company this size. 401k matching is 2%, in stock, and vests over time. Employee discount is a nice gesture, but it's limited to $100 a year (10% off for the first $1000 spent). There aren't any education benefits for anyone at Level 4 (management) and above. Finally, time off is much less than the competition: two weeks of vacation with 48 hours of personal time (including sick time) per year, depending on tenure.
While the stock grant is most certainly a benefit, very few stay long enough for the units to vest. The vesting schedule is accelerated over time: 5% the first year, 15% the second, and 20% each 6 months after that (depending on your level). Most will only see the first year vesting, as the average tenure is less than two years.
The incredible growth of the company causes several issues. First, it makes you feel expendable. Can't do the job? There are 10 more who would kill to have the opportunity, so we'll find someone who can. The promise of stock makes the position extremely attractive to outside recruits; this perpetuates the high turnover rate.
Onboarding at Amazon is extremely ineffective. While several initiatives have been put in place, especially for Operations leaders at Fulfillment Centers, it's still a sink-or-partially-drown situation. We have a saying at Amazon: it's like drinking from a fire hose. I have a saying: it's like trying to drink an olympic-sized swimming pool in a single gulp. The amount of information they require you to know is astounding, and you're given very little time to acquire and understand. Depending on when you're hired, you could have your first yearly evaluation in as little as four months from when you were hired;, barely enough time to catch your breath.
Finally, while it's an awesome opportunity to work with such bright and driven people, Amazon stack-ranks you against them. This hyper-competitive environment fosters rivalry and disharmony instead of teamwork and cooperation. Hoarding of information is commonplace. You get the feeling that everyone is trying to "one-up" one another. Bad-mouthing and double-crossing are a way of life, and you should never open up to anyone. While it's true that your development is your own to control, you rely heavily on information that you will not get as everyone wants to become the SME (subject matter expert).