First we gave a try to MSN: not good, voice quality is so bad... even I was not able to hear correctly.
Skype: Voice quality was good ... a bit louder sound, but again, I was not able to hear correctly due to clipping voice.
Google Talk: today's evening winner! Google talk has been giving good voice quality and no discontinuity during voice chat! its like we are talking on phone.
Update: thanks Huma for identifying typo.