My first experience with XML was in 1998, and at that time, there was an invaluable tool (so I thought) from Microsoft called XML Notepad that allowed Morts to visualize and edit the XML's data in a non-angle bracket sort of way.
The novelty of XML Notepad quickly wore off once the limitations were realized, and I found myself other tools, like XMLWriter and even Notepad, for subsequent XML work.
I downloaded and installed the program, and then started it up. My first impression was that this is still a Mort tool, just with more functionality. It has a tree view of the XML structure, lots of pretty colors, and supports transformation using arbitrary XSLT files. And, the Find functionality is loaded with advanced features, like Regular Expressions and XPath.
But, what I found missing was a true source view integrated right into the program (right now, when you View Source, it launches Notepad). If they could have added a XML view that offered the text editing capabilities found in Visual Studio (including highlighting and IntelliSense), then this would be a lightweight yet fully capable tool that I would find myself using regularly. Until then, I'm not sure what role it will fill in my life.