To my knowledge, once you use EAD, you will become pending immigration status. In other words, your H-1b will be invalid. if you want to resume your H-1b status, you have to return China to get H-1b visa.
I have the same situation, I decide to use my EAD in the end of Jan, 2006. This is my first permanent job because i have been working as postdoc at university since I came to US 3 years ago.