I know two ways to save/load application settings:
I\'d
We use PersistentStore and I can confirm that the data does stick around even after uninstalling and reinstalling the app.
UPDATE: from what I understand, if you persist a non-native object (i.e. you create a subclass of Hashtable and store it) then all the app's persisted data WILL be erased when you uninstall your app, since the persisted class no longer has meaning.