@esumitkumar,
Well, my dad bought the same Karbonn model and has been using it for the last 4 months.
The only purpose was to allow Dual Sim usage at a time. And it worked flawlessly on it. Dont expect anything from the camera. Loudspeaker sound is quite loud to wake up your neighbour's dog!

Service is just good, cause its locally manufactured. The back cover and headphones had some problems, so i took it to the shop and the parts were simply replaced with the new ones. What else you expect?
MP3s play fine on it and the memory can be well expanded to 4GB. See, with ~5K price tag and local(NCR/Delhi) 1 yr exchange guarantee, i think this is just perfect choice for Dual Sim users.