Works well, gray hard to see Rated 3 out of 5 stars
I've been using JS Switch for several weeks now: it does the job promptly upon being clicked, and doesn't bog my ancient system down.
When I tried to teach one of parents how to use JS Switch, I also ran into another color issue: they are used to red meaning "stopped," so they would click it over to gray and get confused when pages broke. Giving the user a few colors to choose from for on & off (like in a drop-down in the preferences pop-up) might be the simplest solution.
Side note (regarding Zenturio's comments): the review system IS supposed to indicate personal preference. As the instructions say on the page for writing the review: "what features you liked and/or disliked...any disadvantages it has." That means that if I find the gray JS hard to see, or if it won't work for someone in text-button mode, we're supposed to include that.