No-one seems to have mentioned this yet? The iPhone4 screen res of 960x640 will be fine. Just means a black boarder around the app 32 blank pixels on either side one way and 64 blank pixels either side in the other direction. So screen wise, as long as you don't mind black borders, then that's ok. But then we have the ram difference (if it's true what we think about the iPad's ram being 256 and not 512) I've not heard anyone talk about this yet.