With the Firefox 1.0 release due soon the extension version has been increased to 1.0 recently. This weekend I updated both the User Agent Switcher and Web Developer extensions to support this and asked for the change to be made on Mozilla Update.
I am also planning on releasing new versions of both extensions soon after Firefox 1.0 is released. For the User Agent Switcher this is just a minor update with a few enhancements, but the Web Developer release will be a major upgrade. You can check out what is already coded for this next release on the to-do page.