Came here after seeing the story on the homepage (and having read a few other articles earlier today).
I didn't think much about it until I actually started paying attention, but I am now noticing issues. I got a XS Max 256gb AT&T on Friday. I have definitely noticed slow loading speeds in apps like Twitter and Facebook when opening up webpages. Cellular reception is definitely poorer than the 7 Plus I came from both at home and work (I have 2 bars at home and 2-3 at work, where on my 7 Plus I have had consistent 4 bars lately). Have not used it to make calls much, but have not had any drop yet, so it could always be a software issue displaying the signal (which I remember happening previously). I was also seeing the WiFi issue other have reported (I am on a Gig/Gig connection at work) and I was getting about 75 up and 100 down. After forgetting/rejoining the network I was back up to 300/300 and have not seen it fall back yet. (Cellular speeds seem on par with what my coworker is getting on his 7.)
Again, this is an AT&T phone so I definitely wanted to report my situation since a majority of issues seem to be with Verizon phones. I reached out to Apple Support on Twitter so we will see what they say.