And that one feature is copy and paste. They will add it when they release the SDK. So that everyone updates their iphones and apple can control who gets to put apps on iphone.
It all makes sense, people will upgrade without thinking if apples adds copy and paste to the iphone. In the process apple can introduce some strict measure so that only they can install apps on iphone. At least that is why they are holding on to that feature. They don't know that iphone application key has been leaked on the internet already.
And here are some of my speculations on how this features will be implemented. Are you seriously going to start a rumor about how this feature will be implemented. I sure am.
I think it will be similar to the home screen jiggly thing. Once you press and hold your finger for a while on any text. You will get a magnifying glass but this time it will be colored yellow and when you move it all the text where it was moved to will be highlighted in yellow and copied on to clipboard. Then just press and hold where you want to paste and it will paste. Let see what apple will come up with. My implementation seems quite user friendly.
The highlighted text color could be Grey or Blue too.