If you have ever dealt with Microsoft App-V, then you know the application packages created during sequencing are not readable. That is why Tim Mangan created a tool that can view modified files and registry settings, and dump out files from the pkg in either text or hex format.
Tim also answers the question "Why do we need such a tool?"
Because things don't always work perfectly. Sometimes files get marked as "application" when what we really need is for it to be marked "user", so the changes made don't roam with the user. Sure, if we know what file it is we can check the sft, but when the app just breaks, we don't always know which file it is to modify the settings to. And then there is all of the .net stuff. Side by side components sometimes cause issues in packages. Before having such a tool, we were forced to just reset the entire user pkg because we couldn't tell what has changed. While you can't edit the pkg with this tool, you can find what changed and use the "/EXE %COMSPEC%" trick to get a cmd prompt inside the user pkg to fix the issue.
And we need such a tool to figure out DSC issues, such as which package is getting the changes.