Also, if you don't have a valid visa stamp in your passport, then before returning you have to take your H1 to consulate and get a visa stamp to enter US. But if you have AP, you don't need.
However, if you travel on AP then you need to travel to/thru' various countries(read immi. officers) which don't recognize AP, for ex. France/Germany. It happened to me, at Houston airport they wouldn't let me board my flight going to "desh" via France, because the bozo in Paris said they don't recognize AP, they needed a valid US visa stamp, even before I return.
In fact if your US visa stamp has expired, and if you don't have AP, it might be advisable to get your stamp revalidated from here, because of the above.
So you have various options...
cheers,
- nik.