"Most of the 'Desktop' Linux liveCD distributions (distros) are
meant to to be used for trying out or demoing Linux before
installing them to your hard drive. Popular distros like Ubuntu,
Mepis, and PCLinuxOS are good examples and in my mind are some of
the best offerings. I've been there and done that. These are great
distros, and there are many more! If you're looking for a Linux
distribution to install on your hard drive, these are all great
distros, and you won't be disappointed. Test drive the liveCD,
install to your hard disk, and enjoy.
"However, many liveCD distros can be used as a day to day
desktop without ever installing them to your hard drive..."