My 2cents.

1. A markup language taking multi-lingual considerations to heart is a must for me. Markdown doesn't work well for non-alphabetic languages in terms of typesetting etc. The web is global and multi-lingual, a new web (if there is one) should be, too.

2. I prefer a new content web rather than a new document web. When I use the web, I absorb and sometimes create content beyond documents. I don't want art communities, for example, to be excluded from the new web. Although an art sharing community can be modeled after documents technically, 'content' is the more apropos. Your mileage may vary, though.