Pros
Fluor is a huge company: that's both its strength and its weakness. The company employs thousands of engineers of numerous types (chemical, process, piping, etc.). Most employees are able to maintain a decent work-life balance, the pay is good, benefits hold up comparatively well within the job market, and the workplace environment is casual and welcoming.
Cons
Owing to the enormousness of the company, the mid-managerial levels have swelled to silly proportions. At times, the bureaucratic stodginess almost resembles that of a large government agency, with all its pointless and tiresome regulations and lack of movement on even simple requests. In addition, Fluor's employment model is built on a project basis: Engineers (and support staff) move from project to project---literally move, sometimes from the Irvine campus to the Aliso Viejo campus to the Long Beach campus. For those employees who seek a more stable long term in a single place, this can prove problematic. Another problem is with the engineering and construction industry itself: it's typically seasonal. This means that you might not pick up another project immediately after you finish your current project, which would force you to collect unemployment until Fluor calls you back in again.