What bothers me most, though, is that transparency has no real meaning on the Mac. It’s just decoration, not tied to any spatial sense that we expect from our experience with the physical world. For example, if you start typing in the URL field in Safari, the menu of suggestions that extends down from the URL field takes on a lighter version of the Desktop color, basically the same “semi-transparent” color in the background of the Dock.
This is ludicrous. This menu isn’t directly in front of the Desktop, it’s in front of the browser window (which is white because I was on Google’s home page when I took the screenshot). There is no reason for it to look like you’re seeing through it to the Desktop. That it looks that way screws up the sense of layering, especially since it still has that shadow around its border.
This post, more or less, has been in my drafts folder for months because it’s the kind of thing that, as soon as I noticed it, I could not dismiss it. It’s a dagger through my eye.
For what it’s worth, I don’t necessarily share Drang’s complaints with transparency more generally on the Mac; I think it’s more decorative than helpful, but it’s fine. But I keep the “Reduce Transparency” setting switched on mostly because I prefer a solid background for the menu bar. The resulting layering and compositing doesn’t make any spatial sense and, especially with a saturated desktop picture, is often jarring.