I've been really pleased with the response I've received to my call for folks interested in working on Notational Velocity. In particular, Christian Tietze, is really doing a great job with his Notational Velocity development. Please support him by downloading his latest version and giving him feedback using the details he provided on his site. You can also leave Christian feedback here at PE in the comments section or drop your own ideas for Notational Velocity features.
I've been personally testing Christian's versions of Notational Velocity, and they are coming along nicely. His latest build supports MultiMarkdown, and he's added a "heads-up display" (HUD), which is a preview window of the HTML (like QuickLook on your Mac).
Great work, Christian!