Today marks three years since I publicly started using Drupal (Version 4.1) to manage this website. In that time I've ended up creating dozens of sites using this great tool. In my own web development experience it has replaced Userland Frontier and Zope which I had spent a lot of time with. There were a plethora of others that I've toyed with like the PHP-Nuke and PostNuke style programs that ultimately lacked the true flexibility of a first rate content management system. Today the project is headed towards a new release (4.7) which promises to be spectacular.
Once upon a time when I worked for a different firm they had just implemented a very expensive content management system from a major vendor. When I showed the implementers Drupal they shook their heads and said that it contained the taxonomy system that put it ahead of the product they'd just implemented. I'll be the first to say I think the implementation was a part of the problem with the expensive system. Too much politicking at the top and not enough project management in the trenches - but this was the most common state of affairs in that shop.