Tools for writing technical specs
===

Currently my organisation uses MS Word to write technical specification documents.  This has the advantage that it is ubiquitous but the disadvantages

* Formatting & layout is very difficult to get consistent
* Very difficult to version control and merge changes

What other options are there for crafting documents.  Ideally I'm looking for

* Easy to learn and pick up 6 months later (Markdown yes, LyX yes, LaTeX no)
* Ability to build a style sheet/template for use across all projects
* Easy to version control and deal with conflicts
* Export to HTML and PDF

With a low priority on 

* No need to purchase extra tools (Adobe InDesign fails for this reason)
* Export to CHM