Very smart people, everything turned up to 11, including politics
Pros
Most of the smartest co-workers I've ever worked with I met at Apple. Everybody is extremely driven and has ambitious goals, and the environment will increase most people's drive and make them more ambitious. Compensation is good. Opportunities to get promoted to leadership positions abound. In my experience, there was very little useless process, though product groups are rumored to be very rigid.
Cons
If you are not a manager, or working on iOS, you will almost certainly work in a cubicle in boring office space. Everybody is perpetually on-call. Your boss will call you at 8-9PM on a Friday night to ask you a question. You will be expected to work some Saturdays/Sundays even if there's no production reason. The pain of this is slightly mitigated by the fact that you know that your boss's boss is doing the same to your boss. Sometimes it feels like you're being tested. Bonuses are a big part of compensation, and it is easy for a manager to hide subjectivity in your performance review which potentially means getting paid a lot less for being liked less. Perks are minimal for the tech industry these days but fit with the "no-nonsense" budget attitude, and I didn't have such a problem with that.