When we launched the Designer Platform, we completely revamped our theming engine to be super flexible and introduced a pretty cool web-based IDE with real-time preview of HTML and CSS changes (and pop-out functionality for dual-monitor development).
It's a huge focus for us going forward -- we'd love to hear your feedback on whether the new changes allow you to do everything you'd like to, or if not, where we can improve.
It's hard trying to make people realise that we're not "DIY" though :) I've just come up with the phrase "DIY for Designers" which I think captures it pretty well. Designers have, for too long, been punished by dynamic web deployments (the "big 3" Joomla, Drupal and Wordpress) - time to disrupt!