Hmm..I've made a stripped down example that only shows the preference value passed in through the script tag: http://imagine-it.org/google/testprefs.htm

You'll see the preference value displayed different for each of them. Just looking at the script for the testprefs.htm will show you the difference. Hidden preferences are useful for saving state, as fubbleskag-- and I'm not sure you can pass that in through the script tag. Seems like they'd have tricky implications.