I looked at that one too, but the user interaction felt wrong. Clicking on a clustered marker shouldn't zoom you straight in on that cluster because it's far too easy to get disoriented - you lose track of where exactly you are on the map. I much prefer the idea of opening an info window listing the contained markers, and allowing you to zoom further by clicking a marker in that list.
I looked at that one too, but the user interaction felt wrong. Clicking on a clustered marker shouldn't zoom you straight in on that cluster because it's far too easy to get disoriented - you lose track of where exactly you are on the map. I much prefer the idea of opening an info window listing the contained markers, and allowing you to zoom further by clicking a marker in that list.