Merci beaucoup ! Warm thanks from a French beginner who has been looking for a simple, convenient and effective way to practice XSLT without (yet) understanding anything about Java and how to use the SaxonB stuff.
I tested version 1.5.7 of this extension with Firefox 22.214.171.124 on Ubuntu Linux 7.10.
The transformation works well and fast with both the built in xslt and the Saxon one, although be aware that you'll need to have the java plugin installed for saxon to work. This should be made more clear in the documentation.
The extension is intuitive and easy to use and does exactly what it says it will do. I did not notice any errors or warnings in the error console.
Minor usability annoyances: Red color in menu item and button texts that end with a question mark.
This is a very handy utility for anyone who knows XSLT, and there isn't anything like it in the add-ons available at the moment, to my knowledge. It has lots of uses, from pulling out a list of all the links on a page to generating a plain-text-only version for text analysis, right through to testing a new version of a Website by transforming each of the pages on the site and examining the results.