Agile publishing shouldn't need to worry about common tools, as long as everyone on the project is using a common format (XML) and common schema/DTD (e.g. DocBook). Each person could work on whatever section of the document they want using the XML editor of their choice (vim, jedit, Arbortext, oXygen, you name it!) as long as there is some validation prior to checking it back in!
What is desperately needed are more XML editors that support RelaxNG. Thank you oXygen! However, we need the more author-friendly tools to support RelaxNG. (Psst! That means you, Arbortext and XMetal!)