DONE ---- Did a full Format C:\ this time, as opposed to upgrading as before, and everything seems to check out. If you end up with either a watermark or a timebomb after upgrading, simply do a full re-install and it will resolve itself. I am still not 100% sold on the idea of this 15th micro point release being the RTM, but I suspect the RTM will be patched released to insiders. By that I mean to say, I suspect on October 17 (the official general availability release day) we will get a small update and the build will change to 16300. Microsoft after all, proved they could do a small micro point release today and they, themselves said they plan on testing more updates on this build too. If on October 17, the build actually does remain 16299.15 or 16299.xx I will be a bit disappointed (not the 1st time coming from Microsoft).
small updates don't change main build number, only the delta number 15 (visibly) but it will always remain 16299.15 under the hood