I never had problems until iOS 6. I got it mostly working after deselecting WiFi Sync in iTunes, applying, re-enabling sync, and applying, then restarting both my iPhone/iPad and my Mac.
Now my iPhone and iPad usually show up when connected over WiFi, but sometimes one or the other does not until I restart the device.
Now my iPhone and iPad usually show up when connected over WiFi, but sometimes one or the other does not until I restart the device.