I know it's been out for a while, but I am just now considering whether I can do anything with CAW. (Not sure I have the patience or the creativity!) Regardless, I was wondering if anything has changed about being able to modify existing worlds. I read a related question from back in December 2009 saying that worlds can only be created, not modified after creation. (I'm aware of the empty lots available in Ambitions, but I can't get them to line up with the in-game streets and was thinking that maybe this could be done easier in CAW.) Thanks!

No, nothing has been changed AFAIK.
You can only create worlds in CAW, and edit CAW files. The .world files you wan see in your "user/docs/EA/sims3" directory (so the installed worlds in your game) and the .world files in the CAW directory are not exactly the same even if they share the same extension. The one in CAW contains only some data, the rest being stored in other files, while the one in your game contains everything (landscape, painting, road, lots, objects...) "mixed" together.
It seems that CAW can't sort those different elements in separate files again. So, it's only a forward process (CAW -> Game) and there is no backward way. Pity indeed!

CAW is in beta at the moment ( no word on its final release, or if it's even going to be fixed ) but who knows what the final version will bring, you may be able to open existing worlds, or atleast import their terrain, texturemaps and roadmaps.

You can't use CAW *at all* if your game is up to date!

Thank you all for the feedback, especially Inge's comment about *not* being able to us CAW with my updated game. Oh well, guess procrastinating works in my favor this time... I won't miss what I didn't have in the first place!

You can add more sizes of empty lots in-game than EA allowed us, by using my new mod at http://dino.drealm.info/den/denforu...php?topic=207.0

So then from the discussion in here i'm going to assume you can't use CAW to add new digsite spawners to China or wherever to be able to fix the FUBAR that EA's last patch did to those then eh? <sigh> oh well. At least I dident bother downloading CAW BEFORE I asked this question. I don't suppose you know anything about useing the digsite spawners in "edit town" at all? I've tried adding them in China and they don't seem to work no mater where I place them.