So, Apple Pay is finally here. Let me cut to the chase.

The good
Well done, Apple! Kudos for showing the way.

Amazing antenna performance, thanks to AMS booster (that has now been dropped in favour of NXP). You can present the phone to the reader in a number of ways, and it still works. BTW, very few people know where exactly NFC antenna is on iPhone 6... That should tell you something. 

Adding a card to Apple Wallet was fairly straightforward (but not as sleek as it could have been). Funny enough, when I tried to add another card on the go using 3G, Apple Pay said "no Internet connection" (although other apps worked fine with the Internet) - the problem was resolved when I connected to WiFi. Is that a bug or a security feature?

The bad
Holding iPhone in a weird way (with my thumb on TouchID, but without pressing it) felt dorky. And unsafe (from POV of dropping my iPhone onto a concrete floor). Especially during rush hour on the Tube. 

Also, the use of TouchID leads to a natural tendency to peak at the screen ("Wassapening?!"). That could break the NFC session and you'll have to start all over again.

Apple Watch should fix some of those UX issues.

The roadmap
My bet is that Apple will change the authentication flow, allowing you to "thumb in" BEFORE the transaction, say for 5-10 seconds. That will dramatically improve UX, especially in transit (shall I patent that?.. Nah!)

Apple Watch 2.0 will cut its umbilical cord with the phone to deliver enhanced usability, in practical terms. I doubt it, though, that Apple would allow for its watch to be linked to other smartphones (remember, Apple Watch is there to sell more iPhone, inter alia).

Apple Pay will lose its sex appeal once the market becomes saturated with other players (no, I don't mean you, mobile operators...), i.e. "when", not "if".

My educated guess is that Apple will open up its NFC interface to cater for other use cases: mass transit, access control (iLock, anyone?!) including cars, personal ID, remote authentication, etc.