Yes, a GUI for settings is nice if only for one thing: so there can be a search box that you can use to search over all the settings to find what you need in a pinch. It's a lot friendlier if I can do something like "Open Settings > Ctrl+F > 'Font'" or whatever than having to go find the manual and look it up.

I don't care about the configuration language so much personally (though JSON is of course pretty lame in a lot of ways for that task.)

You get almost the same effect by typing “font” as a config key and going over autocomplete suggestions.