hi friend...
here's my take
I travelled to Europe in dec 2002,and here's what my lawyer told me..again..U have to get advice from a lawyer..we're just as layman as u when it comes to immigration law,but anyways:
If u have a valid H1B petition and visa stamp,and plan to reenter using that,by all means go ahead.
If not,DO NOT lEAVE USA until u have ur AP.
I had an H1 valid,but still entered on my AP,just to be safe...if something goes wrong,I can always leave US,and reenter on my H1b.
So ..get advice from a lawyer,and stay safe...
good luck bud
cheers
Jack