Pros

Free Red Bull
Wear what you want
Sometimes fun people
Its a free flowing workplace, and there is a bar.
Entreprenerial

Cons

They own you. NO work life balance, only work. Work life balance if your life is WORK.
Lacking in clear ideas of what they want.
Everyone is way too busy to get any useful feedback
Politics between new staff and old ways of doing things.
Basically if you are doing a job that you would do in your spare time anyway its great, but if you like doing things outside of work look out.
There are insane timelines and workloads.

Advice to Senior Management

Not everything can be done overnight.
Give clear priorities to staff.