Some early observations from using the Release Candidate:

• I’m always impressed by the speed of the Ubuntu repositories. They never fail to max out my weedy 4Mb/s Virgin Broadband.
• My D-link DWL-122 USB Wi-Fi dongle now miraculously works without manual setup voodoo!
• Xgl was installed during my upgrade. This can be fixed with the following command:
  

  $ sudo apt-get remove xserver-xgl

  Nvidia users will get dramatically higher performance with the X.org server.

• Compiz is still completely broken. It just about works in Ubuntu, but Kubuntu users had better wait for 8.04.
  • Update!: Wait! Compiz does work! You have to add the following lines to the Screen section of your xorg.conf file:
    

    Option         "AddARGBGLXVisuals" "True"
    Option         "DisableGLXRootClipping" "True"

    Then all that remains is to launch compiz and kde-window-decorator --replace. The result is highly impressive, but quite unstable. There is a bug relating to running out of video RAM, thus getting black windows, that is only fixed in the very latest Nvidia drivers, which you’ll have to manually install.

• There’s a KDE 3 version of Dolphin, known as D3lphin, which is a surprisingly good, clean paring down of the messy Konqueror interface. Just be sure to turn off the gigantic information panel that defaults to dominating the right hand side of the window, unless you have an 80″ monitor and only view directories with fewer than 10 files in them. The bookmarks panel is also strangely redundant since bookmarks can be accessed via a little icon just to the left of the breadcrumb navigation bar. I presume there will be a tree view in the KDE 4 version, along with all the promised visual goodies.
• Something is subtly wrong with sub-pixel hinting. It gives me a headache to look at the screen when it’s turned on.