You can bend Wordpress into an extremely powerful CMS that can manage just about any type of website (I know, I do it on a daily basis). The upside is that the learning curve is probably lower than that of Joomla or Drupal.
However, there are other products that might be better suited to build certain types of sites and, even though they have higher learning curves, they're also probably a hundred times more powerful than a heavily modded wordpress will ever be.
As the others pointed out, the real question is, what type of site will you be building? If you're blog is just that, a blog, and very little more, than hands down you go with WordPress.