like i said a post above yours, i did it. it is of course empty, but with the workshop you can add pretty much everything you want ingame and with the creation kit people can add all sorts of things to it. The big plus for everyone who wants to build anything ingame or with the creation kit is that there's no stuff there to stand in your way. you don't have to remove ugly grass or trees or dirt or clutter... i'm not sure about its size, but it's huge. possibly endless. when you travel to the world you are shown in the middle of the vanilla map. i went ahead and ran in one direction long after i was no longer shown on the map and there was still no end in sight. i suspect it's possible that the game generates cells when it needs them if there are no specified borders. if not, it's still bigger than the vanilla game.