run 2 in unison: yep morgan thats the best way at the start, i have a few clients like that and it has worked effectivly, a recent case is now they take up 2 spots on google, funnily the old site ranks higher even though i have done some good seo work on the new one so "longevity" must be playing a major role in its rankings.
I did 6 "transitions" like this just as panda started, the one i talk about above was during penguin, so i'm not sure if that made a difference as the panda ones all shifted seemlessly.
does that article suggest that 301 redirects are dead because waiting months for it to take effect is ridiculous in this day when google says its indexing 100 mllion pages a second !
tim