In short, you will find yourself spending quite a lot of time pouring over the Drupal documentation while putting your site together. It's required that modules have not just "README" but also inline documentation and how-to-use modules from the admin and user perspective. Other projects should take a cue from the Drupal folks here.
How Drupal 7 compares
How does Drupal 7 stack up against the competition, like Joomla and WordPress? In my experience, you can bend the current crop of major open source CMS offerings into any type of site you want. Want to use WordPress to power a major publication, rather than a personal blog? It can be done rather easily. Want to use Drupal to power a personal blog rather than as a platform for the White House? It's a bit like using dynamite to go fishing, but it can be done.
But as for suitability to purpose, Drupal is overkill if you are running a small site that doesn't require much in the way of collaboration between members. It requires far too many steps to do something simple like enabling a blog and having posts on the front page of the site that are visible to the world. There's a good reason for that, and the flexibility means that you can do more interesting things more easily using Drupal — if you need to.
If you're running Drupal 6 now, should you upgrade? It depends on which modules you're using. In testing Drupal 7 I didn't run into any glitches with the default modules, but you'll find far fewer themes and mature modules for Drupal 7 than Drupal 6.
For instance, I went to find a tool to import entries from a WordPress blog, but couldn't find a stable module to accomplish that for Drupal 7. The one with the most Google juice was tagged for 6.x only, and the new WordPress Migrate module is still "early in its evolution and not quite ready for an official release."
Drupal 7 is a nice improvement on previous releases, and it's a solid, flexible, powerful CMS. If you've been waiting to roll out a new site, don't hesitate to go with Drupal 7 if it meets your needs. If you're already on Drupal, hold off a few more months before looking to upgrade.
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