i am also using wordpress and Drupal. Wordpress for smaller and bloglike websites and Drupal for medium to large sites. Why you want to look for Joomla? Spare your time and develop more drupal skills. Joomla is not bad, but lacks in security and performance to Drupal. Drupal is also more flexible with his taxonomy-concept and especially with CCK and Views Modules. Also it is very SEO-friendly.
Wordpress is not CMS as package.I use drupal, it has lots of free addons which are regularly maintained.Joomla addons are crap most are not free.
Wordpress is best for BLOG sites, but it's not a really CMS. So if you want to build a blog site, you can use Wordpres, but if you need a real website, please choose Joomla or Drupal.
I love Joomla. I can install and build a website faster with Joomla, than I can with any other CMS. As far a the plugins are concerned, they are easy to install and mature. I prefer version 1.0x to 1.5x because of the plugins, but 1.5x seems to be easier for people to use, right out of the box, so to speak. For a simple blog - use WordPress - but if you really want to do other things with your site - Joomla's the answer. I have sites built with both CMS and I greatly prefer Joomla.
Joomla works well if you have bigger plans for your site, such as e-commerce or the like. Think of wordpress as the "little brother" of joomla. Both have their place and do what they do well, but joomla is more powerful in its abilities. This topic about Joomla and Worpdress is a popular one. If you enjoy learning code ( such as PHP ) try out a Joomla installation on your site. You can always have someone else install it for you. The modules and extensions available for it will probably amaze you. If you are not wanting to delve into learning code, and you are looking, as the others have said, for more of a blogging platform, choose Wordpress. Good luck