Are your systems Drupal-specific?

No, not at all. Obviously we have tweaked the various settings of PHP, Memcached, MySQL, and so on to be optimised for Drupal, and we have common configurations in place for Nginx and Varnish to run Drupal websites, but under the hood our stack is a standard drop-in replacement for LAMP.

We have customers who run SugarCRM on our servers, as well as other custom PHP applications. We cannot offer the same level of application support for PHP applications other than Drupal, we'll need you to do your own config tweaking, but you're welcome to use our services all the same.