my experience

My first 3-year H1B1 expired in 10/30/03. I had AP/H1B1 visa stamp and visited China in Oct/02/03. My attorney suggested to hold H1B1 extension. Why? To see what doc I use to enter US. I used H1B1 to enter States on 10/20/03. I told my attorney and we decided to file H1B1 extension. The H1B1 receipt date is 10/28/03. I got my H1B1 renew in March/04. Since you have H1B1 already. As long as you file extension before expired date, you will be ok.

This is my own experience. For safety purpose, you should file extension as early as you can.