i have 2 iMacs using a shared iTunes library located on a network drive (plugged into the Airport Extreme base station). This way no matter what computer you are on, you have access to the one "true" iTunes library.

Here's the rub -- the iPhone apps do not seem to update in the main iTunes library. That is, if I plug my iPhone into iMac #1 and there are Apps to update, and I update them, then later plug my iPhone into iMac #2, the apps are not shown as updated and it wants to update them (again).

I assume this means the app library is not part of the iTunes library? FWIW, I have selected the option for iTunes to keep my "media" organized, so in theory it should be putting everything in the one library.