
Competitive pay, regular bonuses, and 100% paid insurance premiums.
My co-workers are intelligent, motivated professionals who take pride of ownership in what they produce.
The "AHA" moment that comes from understanding and/or applying something new that genuinely helps my work.
There's very little micro-management of engineering work. This facilitates individual ownership, both in taking credit for successes and responsibility for shortcomings. The net result is very empowering.
It was very casual, and my interviewers were very transparent with me about what working here would be like. That was back in the start-up days, though, so a lot has probably changed...