I uncovered a bug when naively recompiling a universal (iPad/iPhone) app with the 5.1 SDK. The app had high-res assets for the iPhone but not the iPad.
Apparently the @2x modifier takes precedence over the -Landscape and -Portrait modifiers, resulting in retina iPads preferentially using the high-res iPhone launch screen over the low-res iPad launch screen (which are optimized for each launch orientation).
So you end up with a mildly- (portrait) or greatly-distorted (landscape) launch image on high-res iPads if you simply recompile. I imagine this is what Apple was trying to avoid, with reneging on what their API docs say about modifier precedence.
Apparently the @2x modifier takes precedence over the -Landscape and -Portrait modifiers, resulting in retina iPads preferentially using the high-res iPhone launch screen over the low-res iPad launch screen (which are optimized for each launch orientation).
So you end up with a mildly- (portrait) or greatly-distorted (landscape) launch image on high-res iPads if you simply recompile. I imagine this is what Apple was trying to avoid, with reneging on what their API docs say about modifier precedence.