Pros
This company is growing tremendously. There are a lot of opportunities available, and the culture of the company allows (or should allow, see below) people to move up or move forward. Benefits are great, pay could be better for some of the people doing the hard work but not a lot of the design. Pay varies tremendously depending on region. Flexibility in work hours is amazing, and they are TOTALLY open to new ideas, new methods, etc., which is great. Having worked under different departments and areas I see +/- under each. It's hard to generalize across the company.
Cons
I've seen some excel faster than others despite similar qualifications. A lot of that chalks up to management preferences. Get under the right person and you can go far. Not mix with your manager and things might be stalled/undesirable. As others have noted, the extreme growth prevents every detail from being covered. A lot of time it feels like we're biting off more than we can chew. But that keeps things exciting, unless you're the person that gets blamed for the ball being dropped because you're overextended and don't want to work 65 hours each week and only get paid for 40. Not everyone is 27 and without a family.