It's hard, and in my opinion you almost have to be "wired" to work really hard to be successful. I don't necessarily see that as a con, but some would. I did a lot of research on Glassdoor before accepting my initial offer with Amazon, and I can confirm that the people who claim it's hard...they're right. BUT...I think it's rewarding from a career progression/growth perspective.
The comp structure is okay - you'll hear a lot about the stock, and it's great when it goes up! The salary before stock is low because the shares of stock that vest are part of your annual compensation - it's not a "bonus" or "additional comp". The "bonus" comes if the stock goes up, which has historically occurred, but to the extent that the stock price levels-out or drops (due to market conditions, public view of the Company, etc.), the comp would be less-than-desirable, and that is currently my concern. My advice on comp is make sure you're happy with the "Total Compensation" number because Amazon generally ensures you will get paid near that amount.
As a made-up example, if you get an offer for $100K salary and 20 shares of stock per year at a [projected] rate of $2,000/share, your total expected comp would be $140K - that's your baseline.
If the stock goes up to $3,000, you make $160K - basically a $20K bonus.
If the stock drops to $1,000, you make $120K.
--Because the $120K is $20K less than your "Total Comp" number, the expectation is that you "should" get additional stock to cover the difference
And obviously, if the stock stays flat, you make your $140K
Amazon has shown continuous double digit % growth in stock price for multiple years, so it's almost the "expectation" now that your actual comp "should be" more than the Total Comp number that HR provides to you, and therefore current-year salary raises and additional stock grants are incredibly rare. This is where people have a hard time understanding...but that's why you should always compare your comp to your initial baseline/expectation. Also, I think a lot of people think that employees "save" their stock and become very wealthy through that process, but you have to remember that it's part of your normal annual compensation, so it's actually not easy to save a significant number of shares unless you're able to live on ~60% of your total compensation...which isn't easy in Seattle!