Vantaggi
The only reason is so-called job security. Even that is no longer true with their iRace policy. Infrastructure is good. Apart from that, its the best deal for relatively older laterals. People from top engineering colleges get a higher role (at entry level without any training) than people from other engineering colleges spending 3-4 years with the company.
Svantaggi
Stupid HR policies. They believe in employee policing, enforcing impractical rules etc. You never get recognized even with best appraisals. Regionalism is rampant everywhere from onsite to promotion. They prefer to hire laterals from outside rather than promote their own people internally even if outsiders are not competent enough. A lot depends on your equation with manager rather than the actual work performed. Salary is very low compared to similar jobs elsewhere. A software engineer with 4 years Infosys experience after becoming a senior system engineer post iRace can see an IIT fresher get a higher role. Their PR efforts don't justify the ground realities.