Boost and system cache
I use Boost for my company website, and have been pleased with the results.

Did you disable "Cache pages for anonymous users" in the performance settings? Did you add the extra settings required by boost in your .htaccess file? Are you only viewing the site as an anonymous user? Have you made sure the /[drupal-base]/cache is readable by Apache, and /[drupal-base]/cache/normal is readable and writable by Apache?

If yes to all the above, you likely have other issues slowing down your site, such as too little overall RAM (or too much RAM allocated in the allowed_memory setting).