This software has come a long way. Personally, I want to see the final release as soon as possible as well, but at the same time would be happy to see at least one more RC if another number of bug reports come forth. Like it has been stated before, do it right (or as close to) the first time! Looking forward to gold.
I've done that, of course.
The problem is that I have to use file/folder comparison tools to find new images in the package and then add them to my custom style's image folder. While this might be relatively easy for new images, it gets pretty hard in case XenForo upgrade contains modified images. We can't e.g. distinguish by file date.
I understand the issue with the upgrade path you described though. Not sure what would be the best (and easiest for both sides) solution.