Smooth Tasks is a totally great alternative to the default Task Manager widget.
No, not because it copies the way open windows are organized on the taskbar on Windows 7, but because:
a) on notebooks with relatively small screens when too many windows are opened (and when one works hard quite often many windows are opened at the same time), it's impossible to see the titles of every opened window (this is what the XFCE panel suffers from and one of the reasons why I never install XFCE);
b) when the desktop theme is badly designed (e.g. on a dark theme after turning off all the effects on KDE, the font color of window titles on the taskbar are often dark which makes reading the titles almost impossible - try turning off the effects on the default theme on Sabayon, OpenSuse, Kubuntu) and you don't know how to modify the theme to change the font color, it's just easier to install the Smooth Tasks plasma widget.
So, if your distro doesn't come with Smooth Tasks by default (and most don't, except for PCLOS) you may see that the icons of the launched apps are unpleasantly small.
Here is how to make window icons on the Smooth Tasks widget larger:
Right click on the widget -> Smooth Tasks Settings -> Appearance -> Task Items -> Icon Scale -> set it to your liking.
For me at 150% the icons look big enough on the panel.