Pros
Most of the staff is kind and cooperative. In general, direct supervisors are smart and supportive. The work had some stressful moments, but most of the time it is very calm. Coffee is good and free on all the facilities. ESO use to send their employees to training. I worked in the desert, in a unique and beautiful place. All the employees enjoy long vacations, welfare and school reimbursement. If you want a monthly salary, excellent benefits in a very stable environment, this is the job.
Cons
Despite the propaganda, their "clients" are not the scientific community, but the politicians that approve their funds and their exceptional prerogatives. From this basis derives all ESO traits: bureaucratic, avert to change and old-fashioned management style. Lots of exciting possibilities wasted by wrong appointments in upper-leadership positions. There is a high viscosity medium to exhaust anyone trying to do any audacious project; a few succeed after years of tremendous patience, once the idea became commonplace. If you want exciting challenges and frontier technology, go somewhere else.