I sent in my Darwinia registration almost 24 hours ago, but haven't gotten a code yet. I don't recall it ever taking that long when I registered Nova or DR.
I expect the servers must've just been very busy or something. In the future, if it takes that long, you should probably contact someone at ASW. Certainly do so before re-ordering. Refunding orders from credit cards is not as easy to do as you'd think.