Quay returns most of the functionality that Leopard removed from the Dock, namely having a hierarchical menu popup from a folder placed in the Dock. It also adds quite a bit more (which I haven't looked into, or needed yet).

I had a substantial workflow around my set of frequently (but not constantly) used apps with aliases in a set of folders in a folder (web, dev, system, etc.).

I had resigned myself to launching everything with Spotlight until I found Quay. It's AWESOME.