Is anyone out there using Drupal for large scale, business critical enterprise applications?
Does Drupal's lack of database transaction support dissuade potential users?
Are there any other lightweight web-frameworks based on dynamic languages that people are using for these types of apps? What about Java portals such as JBossPortal or Jetspeed as an alternative or a Drupal + J2EE hybrid architecture?
We use Drupal for the main corporate brochure and community areas of our website at http://www.tableausoftware.com
It has allowed us to add on a multitude of plug-able features and customize UX to meet our needs far beyond what we could do with either a more bare-bones platform like rails or django better suited for apps.
We still have room to grow for performance tuning, but we have millions of hits a year without a problem. We've made use of Solr indexing to improve search and allow faceted integrated search for site content and knowledge base and support forums. Additionally, our team has been empowered to create content and curate the site without development hassles.
Lastly, with recent community focus on tools like Features and Context we've been able to manage more risk free deployment and workflow/environment management in addition to improved site architecture.
Drupal is great. I've used it for several mid-scale community and personal websites, and so far is giving us very good results. I would support the comment pointing at the over-done or even low quality of the templates of many of the website's we've looked at out there, but then, just hire a good coder/designer that does this nicely for you.
As for the memory issues there's tons of articles out there that would help you in tweaking Drupal's database management. There's even a module called Drupal Tweaks that does this automatically for you. Here is an excerpt from its project page:
Overall we are quite happy so far with Drupal for quick development of the most varied websites and corporate Intranets.
Yes, but...
Word of Caution: Many community-based themes are coded sloppily, which completely negates the efforts Drupal has made to make their CMS secure. Worse still, common practice in theme development is to find a theme like the one you want and customize it. Since code of these themes is shared so freely, a single sloppy mistake can affect many other themes derived from it.
If you go with Drupal (or any other stock CMS), don't just hire some joe-shmo designer to theme it for you. If possible, hire one contract for the visual theme and a php developer to actually build the theme from PSD's
For transactional support and other significant scaling improvements consider Pressflow http://fourkitchens.com/pressflow-makes-drupal-scale
It depends on what you mean by "Enterprise." It's a horrible choice if you're building a supply chain management tool, for example.
But if you mean "extremely high traffic sites" or "Sites with complex approval workflows before content goes live" or "sites that we can scale horizontally", then I'd say yes. There are quite a few very large scale Drupal deployments out there, from SonyBMG's suite of artist web sites to newspapers and magazines.
I too have issues with Drupal's slowness, but it seems that with top notch developers you can get around it.
It's a moderately difficult tool to make a company website with, its a very difficult tool to make an enterprise-application with. But when it comes to open source LAMP CMS's, there is no real competitor.