I just resolved bug 271812, which means you can now get the DOM Inspector for 1.9 products off of AMO. Nightly testers (and future beta 4 users) will notice that it’s no longer included by default in the product. You can get the add-on here! The UI is no longer coupled to the release of Firefox, so we can update things independent of the Firefox release cycle. Certain back-end changes will still depend on the Gecko release schedule, but I think I’m OK with that since that would require shipping binary components if we didn’t want to do that. Binary components are hard, and other add-ons (like Firebug) depend on some of them too. It’s best if they stay a part of layout for the time being.