The default PCLinuxOS taskbar uses "Smoothtask", which initially displays running tasks as a single icon. However if you prefer the old way, this is easily adjusted.
Just right-click on the Smoothtask area (just to the right of the last icon, not on an icon itself) and select "Smooth Task Settings". On the "Appearance" page, Task Items tab, you can expand the tasks (tick the box) and select "all" from the drop down list. You can even fix the width.
There are plenty of other settings to play with.
And if you have enabled compositing in KDE4, and have multiple windows open, including more that one from at least one application, have a look at what happens when you first hover over a taskbar icon, then move your mouse over the "miniview" for that task - or one of the miniviews for an application with more than one window open. How powerful is that?