I've completed the theme functionality on the new site. Changing the look (and width) of the site is extremely easy and fast. The screenshots that you can see demonstrate this functionality although changes to templates are only minor for testing - in the end result the themes will be quite different from each other.
In addition to themes I've completed a user registration process with live java validation of the form fields as you type. This will simplify the process making sure that your passwords match up and that your address is valid etc. The registration process also features validation by e-mail to ensure you don't get unsolicited spam.
Finally - the most important thing I've learned so far is KEEP YOUR CONTENT AND DESIGN SEPARATED. This is the best way to work as changing a theme or page content is super simple once the framework is in place. It's 4:14am now so I'm going to eat something and watch some TV now... then off to sleep.