Today is the first time that the Revision Slider showed up when I was looking at a revision history on my home Wikipedia, en. It is great! It works perfectly. The instructions overlay was helpful although the tool is so well-designed that it is almost self-explanatory. The RevisionSlider is delightfully precise because of those nice end points in yellow and blue. The slider moves smoothly, and supports some of the accessibility features that I have enabled in my browser due to my minor vision issues.
This tool is actually better than those that I have seen for similar purposes offered on for-profit websites. The German Wikipedia developers and UI designers who created this tool did an EXCELLENT job! Thank you for taking care of us so well. I just noticed that you are taking care of ALL of, as this is a RTL accessible extension!