I have now used Crouton to install and run KDE. So I can now run standard Linux programs like Libre Office and Firefox both of which I've installed. I've also set up Wine but haven't tried any windows programs yet.
So far the KDE Linux set up side by side with the Win7 Netbook on the same WiFi seems to download much quicker but I haven't had them connecting to the same source for the same file at the same time so can't tell if that is just luck of the draw or if the Win7 really is slower.
Installing KDE (or whatever DE you want) with Crouton does involve using a terminal and therefore the command line. Also needed to do the same (sudo apt-get install adept) to install the program for doing graphical installs of other programs. After that the only use of the command line is launching KDE.
KDE unfortunately doesn't do that trick about separate controls for the Chromebook speakers and the headphones.