I've dealt a lot with Drupal. If you mostly build your site with core, views and cck; stick to best practices with your theming; and put some effort into theming forms for end users, it can be very powerful. The module API is powerful and has decent documentation, which by itself is extradordinary for open source.

Where you run into problems is:
- There's a steep learning curve, so inevitably your first Drupal project will be a complete clusterfuck that you'll have to clean up later
- Modules aren't compatible between major releases. This can be a big headache and timesuck if you need more power than Drupal core + cck + views
- It runs a bazillion SQL queries on every page load for logged-in users. Performance tuning can be complicated

I'd be interested to hear some detail about the White House set-up.

Just from reading that Slate.com piece, I suspect Chris Wilson's criticism is coming from a non-technical, writer/editor user of Drupal instead of a technical developer, or end user of a Drupal-run site. Some of his criticisms just don't hold water when compared to other software, whether open or closed source.

Details about the set up are slim, but General Dynamics Information Technology, Acquia and Phase2 were involved.