I'm new here, so I got in this poll late.
I think Copy & Paste/text selection (including between apps) is the most important on your list, with push notification and real GPS coming in right behind it.
I'd like to add a couple more though (in no particular order):
1. Proper Color coding in the calendar to allow a match to Outlook calendar categories.
2. Outlook Tasks and Notes sync over the air.
3. Allowing 3rd party speed dialers and contact search apps to include "#" and "*" characters in dial strings to allow automating calling card calls and calls to other voice mail systems. The Phone app's favorites supports it, so why not the SDK?
4. A real "Today" screen view on the lock screen, and accessible when unlocked as well. Intelliscreen is nice, if you're jailbroken, but I'd rather not have to turn off and on the device to get back to that view if the device is already on.
I have more, but I'll stop there for now.