Has anyone had any success integrating CiviCRM into Craft CMS?
I would strongly expect the answer to be No simply because integrating with a CMS is a big task and the only 3 that are officially done are WP Joomla and Drupal as I am sure you are aware. There are however solutions for having CiviCRM separate from a CMS but still have forms etc available eg
Remote Forms
CiviCRM Modular Remote-Access Framework