Vantaggi
Entry level into a lot of interesting and hard to break into positions. Good place to get some initial experience. High level of professionalism with onshore and offshore resources. Easy to move from company as a direct hire to client.
Svantaggi
There is a cultural barrier to moving up in the company. Management is almost completely Indian, and while there is no overt plan to hire only Indians, the fact is that if you don't speak the regional Indian language of your manager(s) (even if they speak English and even if you are Indian), you probably aren't going to lunch with them, and you probably aren't going to move up in the company hierarchy under them. Also, if you happen to be positioned on a project with a difficult client, the management is not on your side. Your sole reason for existence is to please the customer so that the pleased customer can give more business. While this is in fact good business, it also means that this could come at the expense of your own career, so be mindful of your own options. Your colleagues who are here on H1B visas usually have no choice (they are almost like indentured servants) but to work under very unreasonable conditions. Consider moving on if you don't have that constraint.