1. Put an IP lock on the login page via .htaccess so that it can't be accessed from anywhere else but your IP - this one change alone can stop a significant percentage of intruders.
2. Add this line to the .htaccess file at the top level of your WordPress install - <FilesMatch ^wp-config.php$>deny from all</FilesMatch> - it'll make it harder for your database username and password to fall into the wrong hands in the event of a server problem
3. Create an empty wp-content/plugins/index.html file. Otherwise, you leak information on the plugins you're running. One of the easiest ways to break into a wordpress site is to hack through outdated/unsecure plugins. So don't let anyone see what plugins you're running to begin with.
4. In the header.php file for your theme, look for - <meta name=”generator” content=”WordPress <?php bloginfo(’version’); ?>” /> - this line reveals the version of your install. Again, hackers look for wordpress sites that haven't updated to the latest version, so delete this line and don't reveal your site's version.
5. Remove 'Really Simple Discovery' and 'Windows Live Writer' - http://falcon1986.wordpress.com/2009/07/15/remove-unwanted-w...
6. Block injection of malicious code with these 2 steps - http://wpcult.com/wordpress-security-hacks/
7. Whenever wordPress patches a security hole or releases a new version, apply it/upgrade to it immediately
The above steps should stop everyone but the most dedicated intruder. This is a lot more efficient than boycotting wordpress altogether.