Yes, the ability to change the look of Plasma was planned since the beginning. Plasma can use "themes", which are essentially a number of SVG images and files specifying the colors, to change its appearance. A number of themes are already available on kde-look.org.
Right click on your current desktop, select "Desktop Settings" (alternatively, you can select the same option from the desktop cashew) and you will find the option under "Desktop Theme". You can also download new themes directly from there by clicking the "New Theme" button, using Get Hot New Stuff (GHNS).
In an effort to keep the codebase clean of workarounds (if not even hacks), the Plasma developers have decided that features that require compositing to work will not have a composite-less version. The main reasoning is that in the past (KDE 3.5.x), such approaches were one of the causes of the unmaintainability of the code, and also because supporting those features is actually pushing graphics card developers to write better graphics drivers.
If you use kickoff as your menu, right-click on the application icon, and select Add to Panel. If you use Lancelot simply drag the application onto the panel - you may need to hold it there for a second or so before letting go.
Lancelot makes this possible. Click on the menu launcher, then drag Applications as described above. When the popup menu appears, select 'Lancelot part'.
Various parts of the Lancelot menu can be dragged to the panel in this way. Read this description of how to use it.
'Favorites' may be a good choice for adding to the panel
To make changes to the panel you need to right-click on it - and if you have open applications that may not be easy, The workaround for this problem is to use the panel cashew to bring up the panel settings, then you can right-click anywhere on the panel, including on application tabs, and the command will go to the panel, not the application.
Right-click on an empty part of the task bar (or use the method described above) and select Task Manager Settings. In the 'Sorting' combo-box, select 'Manual'. 'OK' to close it. Now you can re-arrange your task icons by holding down Alt and dragging the tabs to their new order. (If you use this alt-drag while the panel config panel is open the whole group of application tabs will move as one.)
Normally Plasma automatically restarts in the event of a crash. If this doesn't happen, open KRunner by pushing Alt-F2 (it should be still running) and type "plasma-desktop". Plasma will be restarted.
In konsole -
kquitapp plasma-desktop; rm $KDEHOME/share/config/plasma-desktop-appletsrc; plasma-desktop
This deletes your plasma settings, so you'll get the default configuration back. If running the 3 commands at once doesn't work, try typing them in manually and wait a few seconds before running the next command.
(Note that the $KDEHOME environment variable may not be set. Try ~/.kde (Fedora, Kubuntu Intrepid, Debian, upstream default) or ~/.kde4 (OpenSUSE, Kubuntu Hardy and several others).)
The Freedesktop.org system tray specification (used by both GTK+ and Qt) which does not define the sizes for system tray icons properly. A new specification which solves these problems has been developed inside KDE and now it is being proposed for a Freedesktop.org standard.
This is NVIDIA's fault entirely, due to their driver not supporting correctly the XRender X11 extension, and it also affects other parts of KDE SC such as Konsole. See this blog entry on how to report issues upstream to NVIDIA. This page contains a few suggestions on how to improve performance.
NVIDIA has released the 18x.xx series driver that can improve performance dramatically with the Plasma Desktop and KDE SC 4.x in general.
Users who have a NVIDIA 6 or 7 series card should add the following lines to their xorg.conf in the "Screen" section, which may improve performance. You don't need to add these lines if you have a 8/9 or above series NVIDIA card, since they're enabled by default.
Option "PixmapCacheSize" "5000000" Option "AllowSHMPixmaps" "0"
There are some other options you can try, which may improve things if you get poor Desktop Effects performance.
Go to SystemSettings>Desktop>Desktop Effects>Advanced, you will see "OpenGL Options", make sure "Bilinear" or "Nearest (fastest)" is set as the "Texture Filter" option. You can also try turning off "Use VSync" there as well.
To work around this issue, you have to change the 2D acceleration method from XAA (X Acceleration Architecture) to the newer EXA. As this involves editing your xorg.conf file, bear in mind that such a modification may damage your system. Do it at your own risk.
To make the switch, edit your xorg.conf file (make a backup just in case) and locate the Device section for your graphics card. Add the line
Option "AccelMethod" "EXA"
before the "EndSection" line. If there is already a line with AccelMethod, change it from XAA to EXA. Save the file and restart the X server.
Notice that EXA is still marked as unstable, and that some other applications such as some KDE3 programs may render incorrectly
For many of its effects, Plasma makes use of the so-called "ARGB visuals". For older video cards, this can mean a severe performance hit. To disable ARGB visuals and increase performance, you need to set the KDE_SKIP_ARGB_VISUALS environment variable to 1 (KDE_SKIP_ARGB_VISUALS=1) before Plasma starts. You can do so by putting a line setting this variable in /etc/profile or in ~/.profile.