Pros
You can do anything you want. Show up late or not show up at all. People drink at their desks as they do work. They have a lot of lunch time meetings so you can stay up to date on the industry. You are free to travel and spend time in different offices. You have the opportunity to work on a vast array of projects.
Cons
There is a lack of management skills. There are a lot of managers, most of them are incompetent. There seems to be no recognition of hard work. You get promoted based on how long you've been there and how well you fit into the ARUP "culture" (which is nonsense by the way). Expect to have most of your day wasted with stupid meetings and horrible presentations about nothing and lets not forget about the horrible office events. This will cause you to spend a lot of extra hours in the office, usually because an unqualified manager made a decision that made absolutely no sense. Of course you can choose not to attend these events and you become the ARUP outsider and miss the chance for advancement.