People who don't use TeX for accessibility reasons might want to give it another look. The tooling has risen in quality and accessibility hugely of late. I use TexPad[1] - which I like enormously.
Otherwise, as another commenter mentioned, there is always Markdown. Combined with MathJax[2] and custom style sheets you see many of the same benefits with greatly increased simplicity. A great desktop Markdown editor (if people don't like web based ones) is Mou[3].
Lastly - the advantage to using Markdown is that if you have to work with someone who does use TeX - something like pandoc[4] can be used to convert between formats fairly nicely.
One thing I think is missing is a "Make" like program to dictate how to combine multiple Markdown or TeX documents into a single document, which folders to scan for references etc. I've seen a couple of home grown solutions - but nothing that really fit the bill.
We do use Git for scientific papers internally. Especially in the proof reading stage we find it is the only manageable way to have multiple people provide constructive feedback to a paper in a limited time frame.
This has caught on with almost everyone (technically minded I should add) who has been exposed to the approach, so I wouldn't be surprised if this started to catch on in the wider field of Scientific publishing and Conference calls.