According to spokesman Joe LaMuraglia, the 2013 Acadia liftgate glass, spoiler, rear quarter panel and rear side glass are all sourced from the Outlook. The hatch is also the same as the Saturn, but that's always been the case, as the old Acadia used the same part.
Now before you rush to judgment here, we suggest you take a good hard look at the new Acadia and tell us you don't think it looks better than the old model. We've always thought the Saturn Outlook was the more attractive of the siblings, so we don't have any issues with GM's parts-sharing tactic, especially considering all these parts are in the rear of the vehicle rather than up front in the all-important "face."
Considering that GM is likely to still be producing service parts for the thousands of Outlooks on the road, this is actually a really good move. Needless spending to refresh the Acadia when this suitable alternative already exists is the kind of smart decision that we hope GM continues to make.