I'm already in a no-root situation on my AT&T S5. Last carrier phone I'll ever own. I keep loading up the Nexus 6P ordering page and then closing it. Wonder if we'll see another Nexus release this year with an 820 Snapdragon and an S7-class camera.
TOP TIP: The stock Global, unbranded, S7 and S7 Edge, G930F and G935F, are fully compatible with AT&T's GSM network and have unlocked bootloaders, no carrier bloatware and will receive the latest updates and more of them, a lot quicker.
Of course, you will miss out on these exciting, extra, AT&T features baked into their, "cloneware"...
AT&T Locker: Cloud storage from AT&T.
AT&T Protect Plus: Cloud backups, device locator and "Pro Tech support."
Device Help: Essentially a wrapper for the att.com help pages
DirecTV: AT&T purchased satellite TV company DirecTV in 2015, and now their app is right here for you
Drive Mode: Sets auto-replies to texts and calls straight to voicemail when moving faster than 25 mph
myAT&T: Access your AT&T account
Plenti: A rewards program in conjunction with Exxon, Macy's Hulu, and others
Smart Limits: Parental controls on times, calls, data, and more
Usage Manager: Track data usage by app
Visual Voicemail: View your voicemails with your eyeballs