H1B employer change from X to Y immediately after H1B approval

Hi Saurabh,

Could you please answer this question of mine. I recently got my visa approved (on Aug 12, 2013). As i was about to make my arrangements for US, some dispute happened between me and my employer. Now i am wishing to find another employer for H1B (and i am quite close to finalizing the same).

So my question is : Is it possible to switch employer even before flying to US. Or is it that you can apply for switching of employers only after landing in US once.

Also please brief me about this h1b transfer process? as in how long does this process take? How much fees is involved et al.