Frequently just tough, but sometimes challenging in the good way.
Pros
Pockets of excellent leadership. Many bright, talented, collaborative colleagues. Broad diversity of project types, organizational strategies and sets of rules can be rendered a positive if staff can tolerate the inconsistencies long enough to distill lessons about effective leadership styles and which types of project work they best enjoy. Benefits are good, work-from-home and flextime options are good, pay is however on the low side.
Cons
Many bright, talented, collaborative colleagues - but there's no guarantee that that is who you will work with every day. On a bad day, this place almost resembles the Stanford Prison Experiment, as reenacted by a bunch of engineers and scientists locked in an office building. My senior leaders seem to believe that lean, hands-off management allows the high-performers to rise on their own. This may be true, but it also turns a blind eye to a lot of bad behavior along the way (some feeling more "entitled" to bill time, erasing and replacing author names on work product, pressuring staff to underbill, gender and minority issues, and externalization of many costs onto employees' unpaid time.) It can be hard to keep your chin up, for sure. I suppose that's worst of it - the garden variety "cons" are tolerable - long hours, living out of a suitcase / rental, unpredictable workflows and frequent management reorgs may mean that you'll have to take on more work than is comfortable at times in order to stay in good standing. Sometimes you'll get paid to do cool stuff, but there's way more paperwork, routine field work and filler than cool stuff. Oh, and compensation is freakishly variable for the same position.