grouchomarx
iPF Noob
The apps will work, but it will take several months before all of them get updated to work with the higher resolution. And some will not get updated, but should do just fine. They probably won't look too much different unless you look real close.
One should expect app updates to show in mass quantities over this coming weekend. I've seen a lot of the developers BLOG saying Apple didn't release the 2X development kits till about a week ago. For example, instapaper will have an update to accommodate the 2X feature early next week.