Depends on what you do as to what I can tell you, but I interviewed pretty heavily with them a few years back.
I was looking at their construction services group in Houston, so that may change what you are seeing or hearing about them.
Positives:
1. 100% employee owned company, no stockholders outside of the employees that the company is beholden to.
2. Consistently ranked as one of the best employers to work with in industry.
3. Benefits are petty good - retirement (401k match), ESOP, bonus, health insurance isn't too terribly expensive if I recall
4. Good amount of backlog and diverse work opportunities
Cons:
1. Salary is probably going to be on the low end.
2. They tout the non-guaranteed, but almost always guaranteed, bonus as part of your overall compensation. And in good years, that's a great thing. In bad years, not so much. I had come from a ESOP company myself and knew the song and dance with that.
3. Depending on your experience, profession, etc., you will likely get some fairly mundane work until you put your time in with them and get some seniority. Unfortunately, that is common amongst most larger engineering type firms. So the super awesome projects they talk about when you interview are likely out of your reach for a while
Overall, it was a tough decision for me to not choose them. I made damn sure I didn't burn any bridges with them when I opted to go with another company, and still maintain contact with a guy that was my mentor that works for them still.