Mobile number portability, I feel, is a giant step towards increasing efficiency of our mobile operators. Although the efficiencies of our operators, especially in the metros, marginally differ from each other, there would be a lot lot of customers who are totally fed up with their existing operators, but are bound to them only because of fear of losing their numbers when they switch opeators. For such people, it would be a great achievement.
Next important thing that might bother some could be 'Portability at what cost'. If the cost turns out to be minimal, we would see huge switchovers.