Pros
Working at Caltech has given opportunities available nowhere else. In a lab position you are encouraged to learn new disciplines and participate in research above and beyond your job description. As a research assistant I was given the opportunity to pursue independent research and co-author several papers. Health care benefits are also generous and the campus facilities and resources (gym, recreational clubs, etc) are available to staff.
Cons
An intense work environment can lead to a feeling that maintaining a good work/life balance is impossible. The situation has improved in the last several years, and there is now more strict enforcement of salaried employees' hours (preventing them from overworking). Salary is not high, and for several years the institute froze raises (including cost of living adjustments).