This is a demo page for the GM bug reported to GM in http://greasemonkey.devjavu.com/ticket/137.
Assuming you have the test script installed and it's functioning correctly, you should see a pop-up show up saying:
Testing GM_getValue: Val2
Under FF2 + GM 0.8.20080609.0 that is what you get.
Under FF3 + GM 0.8.20080609.0 you will get an error console message saying
Greasemonkey access violation: unsafeWindow cannot call GM_getValue
and the popup says:
Testing GM_getValue: undefined
In all cases, I dump the script that I'm executing into the error console as an info message.
If you need the script, it is : test.user.js
Once you install the script, refresh this page to see it in action.