Challenging and at times frustrating, but overall, a good experience.
Pros
The people - So many people have been working there for years and years and years. You just don't find that too much anymore. They stay because they love it, and it's good to work with happy people. The flexibility to work where you want when you want. The industry - These guys have something great and they know it. There is nowhere for the company to go but up. Senior Managment is awesome. They know their stuff.
Cons
Many middle managers don't share the same qualities as senior management. A bit of an "in crowd" mentality type culture. The hours can be tough at times, but they are getting better about it. The culture is moving from start-up to big company. It can be a bit corporate at times, but if you don't mind that, it won't be a big issue for you. Not really a place with set career paths - you have to fight your way up and through.