Joomla Themeing is pretty interesting. I've done a Drupal site shortly after doing a massive cleanup of a Drupal site that was handed off to me in unsatisfactory condition. I seem to learn a lot when I have something that's broken and I need to get it working. My first PC comes to mind...
So anyway I have 3 Joomla sites under production right now with my current employer. When they go live I'll post some screenshots on them here.
My workflow for theming is pretty much:1. Using the comp I construct a home and secondary page in XHTML. Having clean-valid code before you start theming helps a lot.2. Take a copy of the Beez template and rip all of the CSS out. My first Joomla site I tried to hunt-and-patch through the CSS files and pretty much went insane trying to find and fix all of the styles.3. Plug in the CSS I constructed in step 1 and start building content around it.
What's nice about Beez is that it's already tableless XHTML layout. All the standard components are setup and ready for your styles. The main drawback is the use of several CSS files (layout, position, etc). I personally don't like to chase styles around 4 different stylesheets.
Beez on the web: http://www.joomla-beez.com/