I have been a longtime user of the Drupal CMS, starting in 2002 with a dirtbike website.
That website, and the excellent Drupal code quality inspired me to submit a few patches, and perform ongoing development within the Drupal environment.
In about 2004, it because obvious that Quickbooks was not cutting it when managing the amount of stock we have in our Computer store. This problem is the main reason why Stratos ERP exists.
The 4.7 module version worked very well for our business, but was always very tricky to install.
The 6.x code upgrade took quite a while, but is a great leap forward, and to our benefit, acceptance of Drupal has increased massively since the release of the 4.7 code.