Honestly I think part of the equation is the quality of the AP class offered... and that's something you probably won't have any idea of until your much closer in time to signing up for the class. Elizabeth mentioned languages - we've had a great experience with a language class that really didn't offer anything in new vocabulary to my ds but did offer a native-speaker and great conversation in class every day so it was well worth the time invested in taking it. If he'd had another teacher it might not have been worth it. We've also had different experiences with language arts and social studies AP classes re whether or not the class was focused on teaching to the test vs. teaching toward love of learning and deep thought.
Best wishes,
polarbear
ps - I'd tend to make the decision re this class based on what will be interesting and challenging *now* - once our kids get to high school chances are good that they mostly will be wanting to make their own decisions about classes
therefore over-thinking it at this point might to achieve much of anything in the long run.
