Can anyone who has loaded 4.2 beta report what they get when they run an iPhone application with retina support?
iLounge posted the sad answer in their article :
New in iOS 4.2: The Full Breakdown With Screenshots
iPhone/iPod touch Games on iPad. At least for now, games with high-definition Retina Display support do not appear to be capable of running in Retina Display mode on the iPad. They still display with 1X/2X buttons at lower 480x320 resolution.