With some pride I bring you the next version of Package Explorer. The beta given out earlier gave a slight preview of the direction being headed in, but now the application is feature complete and I can show off some more UI and features.
The goal of the 3.0 release is to allow you full editing capabilities for Open XML packages. I've implemented a templating mechanism along with various other great features such as editing relationships.
First let's start with the new user interface. Well, most of it is old actually :)
From the screenshot you see various features. There is a new toolbar with the Format button, which indents the XML and the bar also displays the active document (the one that will open when you press Play). Also note the New button on the primary toolbar. It takes you to a template selection screen. You can provide document templates with full part hierarchies.
Next stop is the Document Inspector. New options here as well. First of all a 'flat mode' view that displays the list of parts without the hierarchy.

You can access various features from here. Right click any part or document to view their relationship file as in the following screenshot.

Sign and view signatures

And the Validation Inspector has been revamped as well. Allowing custom XML schemas to be selected for use during validation.

Then the last thing I'll mention is the options dialog. Use it to change ehr... options. Yes Doug, you can change the font and font size!

That's it for now. You can get hold of the binaries for this release candidate on CodePlex.
To get some idea of the next version. I am thinking about a WPF UI (I need to learn WPF anyway). The UI can be localized. The framework is there, now for the languages.