I love what this extension does and how it does it. It's a good design, and the live updates as you tweak the settings really helps find the optimal setting for each site.
By default the "Keep up with changing content" interval is set quite low, to a few seconds. On slow or very busy machines, this can lead to update problems. If these occur, try making the update interval longer.
However, the "Disable" check box simply does not work. The only thing it disables is the Settings window. The extension continues to apply the current settings to every tab. (It even applies them to the captions that accompany streaming videos from TED, YouTube, and Netflix!)
To actually disable it temporarily, you need to disable the extension itself. I have been doing that, but it takes longer than it should.
"Text Legibility" also lacks site-specific settings, which is a major drawback, especially for productivity sites (Gmail, Google Calendar, etc) that use custom shading and font colours extensively.
I expect the author intended it to be an elegant way to made global decisions for all sites, but made it too useful for users to want to use it like that.
We love having the ability to customize the appearance of each website on the fly, which this extension provides. We would love to be able to have custom settings for each website. Unfortunately, this is a big change in the design, and I'm not sure the author is motivated to make this change.
So dear reviewers, PLEASE BE KIND when asking the author to take that big step, and to put in those hours! This is a free extension, and the work is completely voluntary, so we need to treat the author with respect!