Not the op, but in NYC walking in and out of the subways is annoying... takes the phone sometimes a minute to re-connect to the cell network. In prior phones w/Qualcomm modems the experience was much faster.
Signal not as strong as previous iPhone 6. Drops to 4G more often in town when this never happened with my iPhone 6.
Since iOS 12.1 update, wireless will just stop sending/receiving data while still showing connection. I will now sporadically lose all cellular signal, until I turn airplane mode on/off, then back to 3 bars.
I've only seen 4 bars on this phone once, at the AT&T store when they gave me a new sim card. Promptly went back to 3 bars when I left the store.