Pros
Mastek used to be great when it was managed by the founders, later they appointed many CXOs who only care about balance sheet and their own indulgences. Brilliant people used to be the asset of Mastek but slowly they are all moving on to other organisations. If you are a bootlicker, this is 'the' company for you. You will go onsite without any technical skills or even on technologies other than your skill set! Don't worry about coming back because PMs with shiny shoes will keep you transferring to other onsite projects!
Cons
Mastek has become more of a staffing company because lack of new projects. Management never cares about any of your issues and will throw policy in your face. Their incompetence and arrogance was the reason they had to close Pune office. Almost all of the senior technical people have left because of new policies. Mastek's entire tech stack will be antiquated within next few years. They will throw extravagant RunTime party and spend crores of rupees for few days of 5star hotel experience. But don't expect good appraisals. After releasing increment letters, the respective HRs went on a weeks 'planned' leave to avoid backlash. nice trick I must say.