1) Tata Sky is not the cheapest DTH provider in India. Thus if you are a price sensitive consumer ( most of the Indians are) , you can look for options like Videocon d2h.
2) In case you are going to watch HD channels, Tata Sky offers only 12 HD channels. Dish TV, on the other hand offers 39 HD channels. The important thing to note here is that the user has to pay additional charges for the HD channels. This limitation might not be relevant to many users as most of the people opt for standard and limited channels only.