Not unless you only use the console and not the graphical environment. Otherwise, while the system might come up faster, you'll have to wait longer after logging in, so you really won't gain much speed, if any.
Originally Posted by DWRZ
I don't know whether GDM is faster than KDM. You could try GDM if you don't mind Gnome stuff on your system, but I doubt that it's worth it.
If so, how do I get rid of KDM? Once done, how do I login via the terminal?
sudo /etc/init.d/kdm stop
If you aren't running KDM, GDM, or some other similar program, you'll be promted to login, and once logged in, you can start X by typing startx. You quit X by hitting <Ctrl><Alt>Backspace.
sudo aptitude remove kdm