Perm just approved and I-140 just filed, can go back to China?

Just got my PERM approved and already filed I-140 (EB3).

I am still a F-1 and H1 will be effective on Oct 1, 2008. Can I go back to China and come back to US? Will there be any problem?

I guess things will be different if I choose to come back US before or after 10/1. It is complicated and I really have no idea what might possibly happen. I will appriciate any help or comments.