I thought I read/saw/heard something saying that apps built for iPhone 4's Retina Display would automatically run at 640x960 when installed on an iPad. However, can't find any documentation on that specific feature, and my app still runs at 320x480 when installed on an iPad.
Is there a step I've missed to make this happen? Or did I just imagine this being a feature?
This is not the case; currently, apps won't auto-upscale on an iPad. Perhaps Apple will add this in iOS 4.x for iPad, but certainly there's been no indication from them that they will.
Apps do not auto-upscale, BUT if you have an image larger than the UIImageView you are placing it in, you will get as large a version as the iPad can draw.
I don't think it knows to pull in @2x images, just ones that are actually larger than the space you are placing them into.