Possibility of H1B Visa transfer who has never travelled to US


I got H1B visa issued till DEC 2013 from current employer A. Now i would like to transfer my H1b to new emploer B from india itself( I have never used my visa for any travel to US) . Can you please clarify

  1. Is that ok to travel to US with the old visa stamp of emploer A and new client letter from employer B. What question can face at port of entry if i can travel?

  2. Will the visa transfer be an issue?

3)What if my employer A know abt transfer and can he cancel immmediately?

4)Do i need to got for visa stamping again?

Thanks in advance.