As a digital media thought-leader, you should be using XHTML 1.0 Strict and CSS or at least planning to make the leap. (XHTML 1.1 is a “pain in the ass with no demonstrable benefit” for most users according to Mark Pilgrim, who knows this kind of thing.)
If the web is your business, now might be a good time to start getting familiar with XHTML 2.0. The third working draft of the XHTML 2.0 specification has been published by the W3C, and it’s clear that the specification is settling down and that this draft will resemble the final specification.
Where previous version of XHTML were basically cleaned up versions of HTML, XHTML 2.0 marks some interesting departures — forms are replaced by XForms, frames are replaced by XFrames, and events are replaced by XML Events. | XHTML 2.0 third working draft | Dive Into Mark: Changes in XHTML 2.0