So I tried out the Pay Beta - the downside is they only accept BofA and US Bank cards during the beta and the only one I have is my debit card which I hate using.
Setup was straightforward enough - had to download the Pay app, put in my billing info, take a picture of my card, and pretty much done. It did sit with the authentication messaging/loading for maybe 15 seconds but I guess I'm considered low risk since I didn't have to put in any other info.
I did get an automated email from both BofA and Samsung for the card add which doesn't hurt.
So mostly b/c I didn't want to use my debit card much, I made just 1 transaction at a convenience store that didn't have NFC. Once Pay is setup, you see this tiny bar at the very bottom of your lock screen. You swipe up, your default card is shown, you fingerprint, and then you place your phone next to the area you swipe your credit card.
Surprisingly...it worked. The cashier was telling me phones don't work and then was surprised it ran through normally.
I've already disabled Pay however since again, I hate using my debit card. The good news is most of my cards are Citi cards which is a supported partner so hopefully I'll be able to use them for the live product. However, at first glance, it works pretty well. NFC I assume would be pretty much the same - tap instead of holding next to the swipe area.