I have been in a similar situation
My initial visa stamp was for company A. Then I started working for company B, and subsequently for company C. While I was working for company C, I went to my home country and got a new visa stamp, which I used to enter the US. I used it again to enter after a business trip abroad. This was pre 9/11.
A few months later I moved back to company B, and continued working for them on the basis of the intitial H1B approval. I visited India again just a few months prior to the expiration of my H1B approval with company B.
I admit to having been very nervous, though I consulted my lawyer prior to my departure. Based on her opinion and advice, I carried all documentation related to my initial H1B approval, my second H1B approval, my third H1B approval, my I-485 receipt paystubs for all transitional periods, and a letter from my current company stating that I was currently working for them and that I had a valid H1B status. I may add that company B had sponsored by green card petition prior to my moving to company C and the petition was in effect even while I was working for company C. This was post 9/11.
Not only did I not have any problems in entering, I was not required to show any of the documentation (except perhaps for the H1B approval for company B).
This was my experience, and hopefully it would provide you with some information to base your decision on. As always, I would recommend consulting a lawyer before taking any course of action.
Best of luck!!