What do you like most about LiveJournal?
Creative expression: that I can use lots of avatars I've made, and that I can make my own mood theme
and enjoy using it, that I can have my own art for header or sidebar images, thanks to the variety and flexibility of the different journal styles.
I also very much appreciate that people (family members, etc) don't have to get their own LJ accounts (or be signed in) in order to read my posts and keep up with my life, unlike certain vile horrid places like Facebook. =P I also like the comment-filtering features that allow me to screen out most spam comments so visitors don't have to see them.
That I can pick my own userid and that I can change it. I HATE sites that try to force me to use my real name; won't do business with them.
And I love that I can get (currently 4) paid accounts, so I and others don't have to see horrid ads, and I can enjoy the perks listed above.