Pros
Project I worked on had the opportunity to work up to 20 extra hours overtime for time and a half each week. Project was interesting, they provided 24/7 accommodation and subsistence for every day worked, had opportunities for training (survey, photogrammetry, skeletal excavation).
Cons
You were expected to work 10 hour days 5 days a week with an option to work another 10 hours on Saturdays which is good in the short term but incredibly draining long term. Supervisors and up were 'expected' to work a certain amount of Saturdays per month despite the fact that you can't force people to work over 48 hours a week. Office staff (HR, admin) were hard to get a response from and there were numerous problems with staff accommodation that seemed to get ignored; threatening bailiff letters about energy bills, power outages, flooding, unauthorised access to properties with no warning by landlord contractors.
Bought some new branded company vehicles during the project (including a Range Rover) but then didn't want to pay staff double-time rate (as written in contracts) to work a Sunday Open Day for site.