In terms of adaptation of WordPress and getting more people to use it, I feel that its lack of custom post types and write panels, a la ExpressionEngine, is preventing WordPress from powering larger sites. Sure, WP just won the open source CMS award, but the core of WordPress is still built as a blogging platform - posts and pages.

If we could start customizing different types of posts and creating additional write panels, WordPress could do SO much more. Almost every theme I code requires the use of custom fields for posts, and often the client gets confused or puts content in the wrong location. Native support for custom write panels would open up a whole new realm of content creation through the WordPress platform.