Pros
Compensation package includes health insurance, gym, cellphone bills, free meals and taxi for late after-hours, maybe something else, which I didn't use. Project bonuses are likely. Salaries are revised twice a year. As a software developer/consultant I enjoy working with competent and motivated people. Projects are rather diverse, you get an opportunity to both expand your skills and deepen your knowledge. Flexible hours are likely but it depends on the particular project. Inner processes are conducted with very little bureaucracy and the atmosphere is healthy in general.
Cons
Your experience and growth will significantly vary with the project you'll be involved. Current appraisal approach works in favor of indispensable employees irregadless of their skills. Office is not as nice as you'd expect from a large IT company.