Also you might want to update how you read user IP. For users like me who are using cloudflare on their server, your plugin was showing the server IP as the user IP.

Here’s code from another plugin WP-PostRatings that correctly returns user IP.

public function getRealIPAddr() {
	foreach ( array( 'HTTP_CF_CONNECTING_IP', 'HTTP_CLIENT_IP', 'HTTP_X_FORWARDED_FOR', 'HTTP_X_FORWARDED', 'HTTP_X_CLUSTER_CLIENT_IP', 'HTTP_FORWARDED_FOR', 'HTTP_FORWARDED', 'REMOTE_ADDR' ) as $key ) {
			if ( array_key_exists( $key, $_SERVER ) === true ) {
				foreach ( explode( ',', $_SERVER[$key] ) as $ip ) {
					$ip = trim( $ip );
					if ( filter_var( $ip, FILTER_VALIDATE_IP ) !== false ) {
						return esc_attr( $ip );
					}
				}
			}
		}
}

Thanks.
Please consider adding title attribute to your li elements to display the hover text as a tooltip text.

Also it would be nice if you can provide option to change the star color on mouseover event as well in Style – Rating Widget.