Recently I've been doing some more "in depth" work with Drupal and I must say I'm very impressed with the power and flexibility of the software. My only problem is that it takes a little while to get my head around some of the new concepts and terminology that Drupal uses. Coming from a WordPress background (in terms of my most used CMS) I'd say that Drupal is the better choice for any significantly complex CMS site, while WordPress is much easier to set up and use for a more blog-oriented site. If you haven't checked out Drupal yet, do yourself a favour and have a look. To save some time and hassle, just install the CCK and Views modules straight away – they're very handy to have.