As seems to be common with tools these days, installation is really quick and painless. Just fire up your favourite shell and enter the following.
curl https://raw.github.com/wp-cli/wp-cli.github.com/master/installer.sh | bash
You might want to install it to a custom path and then link it instead
curl http://wp-cli.org/installer.sh > installer.sh sudo INSTALL_DIR=''/usr/share/wp-cli'' bash installer.sh sudo ln -s /usr/share/wp-cli/bin/wp /usr/bin/wp
If you're on OSX and running Homebrew then you can use that instead!
brew tap josegonzalez/homebrew-php brew install wp-cli
Using wp-cli to install Wordpress
In your favourite shell, cd to the installation directory and download a new copy of Wordpress.
cd /my/site/directory wp core download --version=3.6.1
Next we'll need to set up the options in the config file.
wp core config --dbname=mydatabase --dbuser=myusername --dbpass=mysecurepassword
Finally, run through the install to setup the database and everything else.
wp core install --url=mydomain.example.com --title="My Example Blog" --admin_user=myadminusername --admin_password="myadminpassword" --admin_email="firstname.lastname@example.org"
And that's it! Happy hacking!