I have my iPhone 5 and I am selling my 4 today. I am pretty confident that I have all my content from the 4. I recorded my old VM onto the voice memo on my 5. Unfortunately AT&T does not transfer VM. So I think that was the only thing I had that did not transfer over. I have my 4 backed up from when I activated my 5. I assume iTunes keeps this information? Now my backups are with the new phone, but just incase, I still have the 4 backup as long as I don't sync it once it's reset, right? I have never had to erase my content before, so it makes me a little nervous, but I'm sure it will work ok. I am actually getting my 5 replaced because the Home button has not responded on a few occasions, so Apple was quick to replace it. They are sending one out.