A rock-solid CMS with access control levels for multiple user groups.
Pros & Cons:
Drupal is my choice for a CMS when you need good ACL (access control levels/lists, ie multiple user groups) and a rock-solid CMS. It's true that eZpublish and Plone are stronger in the ACL area (and several others), but the server restrictions or cost implications rule them out for inclusion here. Drupal will supply all normal requirements in the ACL area and most other small/medium enterprise functions such as versioning.
Its strong points are the ACL capability, stability, scalability, and solid reputation for trouble-free performance. As a standard PHP CMS, it can be installed remotely on any LAMP server (the most common type). It is highly extensible, and a variety of distros are also available that package sets of modules and install a typical site profile such as an online magazine or a college site.
The negatives aren't really negatives at all - they are simply areas where others perform better. Here, we have the relatively low number of plugins, including templates, that restricts both appearance and functionality to a certain extent. Next comes the very basic backend admin, which contributes to some usability issues in this area. Finally, and probably the biggest negative, the way that ACL capability has made many backend admin functions obtuse.
However, these are simply areas in which others do better - and no other CMS in this class does them all better or we'd be looking at that instead. Drupal is the #1 choice in PHP-normal CMS with ACL and that handles business tasks well.
It handles high page numbers better than Joomla as the structure is better for this. High traffic is handled of course, but this is a hosting issue in reality. Keep in mind that this type of CMS is basically a PHP script, and there's not much stopping one of those from churning out tons of pages a second - if the load-balancing arrangements can support it.
Multimedia capability depends on plugins, and they aren't present in sufficient numbers to allow wide and complete support; but Drupal has enough to do the usual jobs. There is a recurring quality factor in this project that means instead of lots of plugins and some being of low quality, there are less - but the quality is overall of a high standard. For example, three bridges are available for the vBulletin forum.
Content categorisation is stronger in Drupal than for most CMS, due to the useful and interesting taxonomy. Using this function allows the stratification of content according to user-defined terms and classes. If the normal 3-level CMS content structure doesn't suit you (section / category / item), then Drupal will allow other methods. It also has built-in SEF URLs, which is a major strong point, especially as that removes the usual CMS issue of multiple addresses for the same page.
Drupal is a fine business CMS, and a good small-enterprise CMS - but probably not a large enterprise-class CM system. That is because although it has good ACL and versioning, the other components necessary for this appellation are not present or good enough: workflows, audit trails etc. For this profile you could plug it in, or perhaps more likely, go to an extended eZpublish solution or Alfresco - and unless you are a CMS developer, costs will be appreciable.
Documentation is good, with PDFs and books aplenty. Because of the widespread commercial use of Drupal, things are well organised here.
SEO potential is good (now). In the past, with session IDs and all that palaver, things weren't so good. However, nothing moves faster than CMS projects right now, so what is true one year is completely wrong the next - just check forum posts on these subjects and you'll see that clearly enough; statements people made last year are well outdated now. Drupal is a good choice for an SEO-friendly CMS - not as good as Joomla, for practical reasons mainly, since in theory it's actually better.
Drupal is a strong, straightforward CMS with good ACL. It isn't easy to use, though, since as soon as you add ACL into the mix, admin usability tends to go out of the window. At present its capabilities lie in the provision of a robust CMS with multi-group page and section ownerships; the useful taxonomy capabilities; and the general air of quality surrounding everything in this project. This is not a second-rate product, it is of the first quality. It scales really well, and is rock solid with high page numbers and heavy loads. With a top-class server admin you can get over 100k visits per day out of just one dedicated server - we do.
In the future, the existence of more plugins will allow better functionality. We like Drupal a lot - it's what we run Gizmo's Freeware on. With over 100,000 visitors a day now, and rising steadily, we need a solid solution. If I have one major criticism of Drupal, it's the templating system, which is notably poor compared to Joomla.
Other CMS in this class are:
Both these are more capable as an enterprise-class CMS than Drupal but are more expensive to run, as they won't live happily on a standard shared LAMP server - eZpublish because it doesn't use the normal form of PHP acceleration, and Plone because it uses Zope as middleware, ie as an application server. On a dedicated server, these apps need someone who really knows what they are doing.
Drupal was reviewed by Gizmos Freeware on based on version 7.0.