I've been working with Drupal in a professional capacity for about seven months now, and I have to say that the biggest hurdle for adoption I am seeing is the inability for Drupal to gracefully deploy from development to staging to production servers. This is something I've been struggling with for months now, and with my current project being as large as it is, and having multiple developers, all working from different sandboxed environments, as well as multiple staging servers for both in-house and client review, this is becomming a huge down-check on using drupal for further projects.
