Very strong Bluetooth performance with no problems. I picked up the new BeatsX earphones and am enjoying this combo. Screen is really good and the phone is very fast at pretty much everything.
I just sold my old phone (a 6 Plus) and am very glad I made the move. Definitely worth the upgrade. Even with the new iPhone 8/X/whatever coming out later this year, I realistically wouldn't upgrade until next year anyway as I don't like first run models of anything and usually wait a few months after launch to purchase.
I sold my iPhone 6s Plus as well, but what ios are you on? My Bluetooth wont connect to anything other than my watch. I think this is common in iOS 10.2.1 though.