Pros
Generally good, smart people, some large and interesting projects for well-known corporate clients, ample flexibility to work from home or work your own hours, as long as you hit your billability goal (unless you're a junior person doing lots of field work, which is more rigidly scheduled). People who are driven and really care about doing good work and meeting client goals. Generally, if you're a good person and you do good work, you'll get noticed, get plugged into projects, and get promoted very quickly. You can carve out a niche to do whatever you find interesting, if you have that entrepreneurial drive and can market yourself well enough internally or get lucky (easier said than done).
Cons
Sub-standard salary as an engineer (not sure about other disciplines). Heavy emphasis on billability and sales. Heavy emphasis on H&S training -- but no training on technical topics unless you seek it out or employees bubble it up themselves, and even very little project management training which is a core service. If you don't have that aforementioned entrepreneurial drive, you may find yourself on work you don't like, or lacking work. Benefit perks such as automatic overtime bonuses have been chipped away over the past 5+ years. LOTS of corporate gobbledygook communications-wise. Lots of internal emphasis on the soft-consulting fields like sustainability and social consulting -- yet the majority of the company are hard technical folks in remediation, air pollution, etc. Tied their wagon heavily to oil companies, so when gas prices are down ERM is down. How much you know about operations and how much you are plugged into work can depend heavily on the partners you work under -- they can be something of a black box collectively if you're not connected with an open one who shares. Company runs "engagement surveys" but never makes any of the suggested fixes, or cherry picks easy/soft problems to solve. You may get lost in the mix in some of the larger offices -- there is a big difference in culture between offices in some cases. Lots of hyper-corporate jargon. Ultimately, a company that is mostly an environmental technical and regulatory compliance consultancy but wants badly at the top to be a management consulting firm.