I’ve been using Linux for over a decade and I have been using Kde as my desktop environment almost as long. I nearly fled the ship after the rocky transition from 3.5 to 4, but I am now back fully onboard with it. I do, however, have two minor complaints. The first is the taskbar. I like my taskbar to be quite large, so I can have two rows of open applications, but I find changing the size of the taskbar to be sketchy at best. Last night while resizing the taskbar so I could see firebug better, all the icons on my taskbar disappeared with no way to get them back. I tried various things but in the end, i decided I should just go back to the default taskbar and re-customise. I have had to do this numerous times and so knew how to do it, but I remember the first time I went searching for how to do it, it took me ages to find the right advice. So here, for your viewing pleasure, is how to reset your KDE task bar:
$ kquitapp plasma-desktop
$ rm ~/.kde/share/config/plasma-desktop-appletsrc
$ plasma-desktop &>/dev/null
This can be run during a session and will be persistent after a reboot/logout. You can now customise your taskbar the way you want.