Just thought I would throw in an idea. I am pretty new to editing php/css, and have been getting my feet wet in customizing a blog. A ton of what I do is trial and error, as I imagine it might be for many people, and I find myself keeping a weird backup archive on my computer of the files I'm editing. Things get messy when I revert to an older version, etc, etc.
I am wondering if possibly implementing a history/revision function to the page editor could be a possible feature for WP in the future.