The thing I liked best was the autonomy to a certain extent. I answered to myself for my success and I was given the tools for the most part to meet the requirements of the job. I also got to work with very bright people. I got to work over-time.
Cons
My direction was not always clear. Things would change almost daily in terms of priority which made it hard to complete tasks in one day. (This was where the over-time was good) The CEO was not very communicative sometimes. After my boss quit, I did not get a meeting with him for several weeks. I had to re-do a lot of work for that reason.