I upgraded from a 6+ (128 Mb, iOS 10.2) to a 7+ (128 Mb) yesterday mostly to get the new camera. I also have an original Apple Watch Sport - from October of 2016 - my 60th birthday present to myself. (The Watch has WatchOS 3.1) I had/have three credit/debit cards set up in Apple Pay on both the phone and Watch. The last transaction I used Apple Pay for with the old combination of iPhone 6+/Watch was to pay for the new phone. I had backed up the phone to my MacBook Pro just before going to the Apple Store and took it with me for the restore, which was done in the store while I was there. In the course of the process the Watch had to be wiped/restored as well to pair with the new phone (or so I was told). The whole process took a couple of hours (the 128 Mb phone had 50-something Mb free). In the end, I came away with a nice new phone with everything on the phone appearing to to have been tranferred to the new device and functional, including all three cards reinstated in Apple Pay - EXCEPT that one card refused to be added back on the Watch and another needed to be "verified" in order to be made functional on the Watch. Getting these last two pieces of the puzzle reassembled was frustrating and time consuming. The technically simpler one - the VISA from my credit union which needed to be "verified" took several calls in which I was shuffled back and forth between "member services" and the VISA people before they finally did something in the background while I was on hold and it was working again. This one I don't think was an Apple issue, per se - just something BECU wanted. The other one (Chase Amazon rewards VISA) was another story. I tried, repeatedly, to add it via the Watch app's Wallet and Apple Pay section. Each time it asked for the CVV, gave me the terms to agree to, I agreed to them, and then it considered for a few moments and told me it couldn't add the card and suggested I contact the issuing institution in the resulting dialog. So, after the BECU saga was done, I called the Chase credit card number. The first person I talked to could not find anything wrong and she sent me to their digital wallet people. This person also could not find anything wrong at her end and really could not offer me any help. She various times told me I had to delete the card from my Watch (couldn't delete what was not yet added), delete the Watch app from my phone and reboot it then reinstall it (no way!), and then, since we talking were ON my New iPhone, she cajoled me into hanging up and restarting the phone and trying again to add the card on my watch. So I did - and it didn't make any difference (though the app thought about it for awhile longer before telling me it couldn't add the card to my Watch). In the end I fixed it myself by doing what I thought about doing before calling Chase in the first place. I deleted the card from my Wallet app on the iPhone, then re-added it. I started with the Watch this time, and it went right through. Then I put it back on the Phone, and that went right through. How the heck it got "out of synch" (the second person at Chase's suggestion) I don't know but it did. This is the one that maybe needs to be put on the iOS things-to-look-at list. In general the device upgrade process went smoothly (though it took a couple of hours) but the Apple Pay hooks didn't make the transition across device pairings as smoothly as they could have. This experience will give me pause when contemplating the next upgrade in a couple of years or so I am sure. So..... heads up if you are an Apple Pay user with the Watch and you get a new iPhone. It may be a frustrating experience, at least for awhile.