Yea but can't you use canonical tags on the original site so Google's index is updated with the new URL, thus avoiding duplicate content problems?
This was my thought, as well. It seems like a safer, softer way to test out the transition.
So no redirects for anyone going to an old URL?
I would definitely set up 301 redirects to get the user to the new domain but from for concerns purely about duplicate content, the canonical tags should be sufficient enough to prevent page rank damage.
You can actually mark one of the URLs as canonical if you want to keep both sites up.
What if you returned a 301 to the new URL? You'd think Google would have logic to get that kind of hint.
That's probably what he did - it's the best practise, I believe.
I think they do. If you setup 301 wildcard redirects, google should replace the old site's urls with the new one in their index over time, after they've been crawled. (at least from what I remember when I was digging into it myself)
The old domain (saveyourself.ca) mentioned in the article does do this.
That was the whole point of the article ;) how that didn't work and how it fucked his site.