XWindows Dock is a better Leopard dock clone for Windows
However, one small failing right off the bat is that XWindows Dock doesn't support drag and drop - which might be a deal breaker for some users. I don't change my dock icons all that often, so I wasn't put off by the few extra seconds required to browse for my go-to programs.
PNG icons are supported, and the dock's effects are configured in myriad ways. Icon size, transition effects, transparency, zoom level, reflections, shadows, and much more can be precisely tweaked. You can also choose to display your dock in a 2D or 3D view.
Leopard's stacks feature is also built in, and the Dock will automatically choose the best viewing style. You can specify manually of course, with grid, fan, gallery (pictured), and list views available.
One other shortcoming of note is that you can't change the location of XWindows Dock - it sits at the bottom of your screen. Development is very active, though, so maybe we'll see drag-and-drop and repositioning options soon.
The developer states "no other Windows application of this class has so many graphical subtleties such as reflections, transparencies, shadow and blur in a single package," and I'm inclined to agree. If you're using RocketDock, try XWindows Dock and let us know how you think it stacks up [insert groans].