The Vectra platform also underpins the Saab 9-3, Chevrolet Malibu, and Pontiac G6, which are all sold here in the US.
It doesn't surprise me that Saturn restyled a Vectra for it's flagship, since the departing L-series Saturn was a revised MkII Vectra. The new Aura is quite a bit nicer than the outgoing L.
Just this week GM announced that the Astra will replace the unloved Saturn Ion for 2007. The Ion, which rides an earlier version of the Chevy Cobalt Delta platform, has been a big fat dud all around. We'll be better off with the Astra.