Smooth Tasks is a task manager for KDE which supports grouping and I think almost all functions that the Windows 7 Taskbar can give. It has more advanced thumbnail preview than the default one by compiz. It is the KDE equivalent to DockbarX, or should I say more than it.
Smooth Tasks can be customized upto your choice. For example you can choose windows to group or keep separate, keep certain windows expanded and more. It also has smiliar features as Aero Peek.
You can also display only the application icon or the expanded mode. Which is the feature I longed for in DockbarX. Also you can choose icons to only expand if you hover them or if they need attention.
You can find Smooth Tasks in your package manager or download here.
I feel that although gnome is said to be more stable (Although I rarely experienced any crashes in latest versions of KDE), KDE gives more eyecandy and being based on Qt, there will be a lot more advanced applications available for it.
Smooth Tasks - More than a Task Manager for KDE