A friend of mine runs a Czech community-website for naturists at http://www.naturista.cz, and he decided to switch from just HTML-writing to a CMS. Drupal 4.7.3 was installed, and we got to the work of starting all the things. We were both beginners, and the experience was like this: Drupal is really powerfull, but its whole design is somehow different from today's standards for user-friendly page, our users say. The discussion forum doesn't look like they are used to, to say it simply, plus some minor ideas around (can't understand, why a discussion-topic is split to first message/comments being different content-types!). Also we (authors of the site) had quite a few problems with unclear structure&descriptions in the admin section, which is ofcourse just beginners' problem, but still a problem, even a few bugs... But still we think that Drupal is the best choice available.
The biggest problem for us was a reasonable theme - finally I managed to create one, so that's why I'm posting to this place. You can check it at http://www.naturista.cz - pretty simple in fact, but still it took a lot of time, because I just learned PHP and CSS on it. The experience in this part is: Drupal is not easy for beginners. Overriding Drupal's CSS requires you to style simply EVERYTHING with high specificity, no simple script!