I've set up at least 50 Joomla websites in the past 3 years and at least as many WordPress blogs. Both platforms have very strong, active communities that are constantly improving the products based on community feedback.
For small sites WordPress has become a viable solution which I wouldn't have said a year ago. Many new plugins and tool have appeared in the past year that make it easier to build a website instead of just a blog.
Joomla has matured and the release of the 1.5 platform last year solved many of the problems with the original version. They rebuilt Joomla from the ground up instead of patching the previous versions. Search friendly URL's are now built into Joomla and my Joomla sites appear highly ranked in Google with little effort. Adding SEO plugins to WordPress also makes it fairly easy to rank high in the search engines.
I still prefer Joomla for larger sites because I haven't found a good menu plugin for WordPress that lets me create menus with many levels that looks clean. . Joomla lets me create multiple menus located at the top, on the side and at the bottom of the website. I haven't been able to create multiple menus in WordPress without custom programming. 
I like the way Joomla lets me move content around in different module positions and I can define the module positions in the template. WordPress is limited how you can display content. Widgets must appear in sidebars and it's not as flexible as Joomla. I know you can create custom themes for WordPress but it's always the main column and 1 or 2 sidebars. I'm sure WordPress will continue to evolve and become more flexible.
WordPress was designed to be a blog system and evolved into a content management system. Joomla started as a content management system and continues to grow. Both systems have easy to use Admin interfaces but Joomla has a lot more features so it looks harder to use than it is. It's like Microsoft Word. You have 1000 features and you use 10 of them most of the time.
To sum it up, I like both platforms and I'll continue to develop sites in both platforms based on the client's needs.
