I think Magento is great and it should be possible to integrate with Drupal, but to make this work well would be a very complex project.
The level of integration that you would want in such a combo is probably most closely matched by vbdrupal. VbDrupal is very powerful but also quiet a resource hog. Disclaimer: I last used VbDrupal about a year ago so maybe it's not slow anymore. A Drupal-fork would also be undesirable.
In the relevant Drupal group a proposal was posted for the integration but I think such a proposal should be preceded by a research of the feasibility of the integration and an analysis of what would be gained/lost on both ends (mage/drupal) when they are integrated.