couple things id like to see (not really needed but hey...) more control over what app icons are shown. For example with standard apple apps such as news stand there should be the red X to delete it, but a menu in the settings folder for re-enabling these apps.
siri available for iphone 4 and 3gs users but thats probably what you would call a 'big' change
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the ability to change the theme would be cool too, even if it was just basic changes like colour and transparency so that, for example, you could change the colour and transparency of the dock at the bottom and the lock screen items like the unlock bar and clock bar.
also widescreen backgrounds like with android would be really cool, so as you move across to other pages on your main screen the background moves along with it. I cant really understand why this hasnt been done before.