As for osCommerce, I started down the path of customizing the templates and layout, and started to get fed up. I’ve been using XHTML for over 5 years now, and when I have to move code from HTML 4 to XHTML that’s not much fun or a good use of my time. Since Zen Cart is a fork of osCommerce, which is much closer to a standards-based application (XHTML+CSS) I switched. More on this as we get deeper into it.
One of the strengths of WordPress has been that they say they “focus on aesthetics, web standards, and usability” and while this isn’t always 100% correct, it’s mostly correct… enough to allow you to not worry about the details and focus on what you can do with the application.
Exciting times we live in, eh?