Working with Ruby 1.9.1 and Sinatra 1.0a has been an awesome experience. I've learned a lot, and was ultimately successful in getting the Regdel demo to run.
I even got to use the new tilt interface to get basic markdown support (with rdiscount even), simply by adding this basic helper:
def markdown(template, options={}) output = render :md, template, options '<div>'+output+'</div>' end
I'm wrapping the output in div tags so that the output is a valid xml document and can be transformed via xsl.
This is getting to be a really awesome platform. Seriously.