I’m actually back on 12.4.1 with my 7. I upgraded to the GM and my 7 was getting really hot and all my messages photos were “indexing” as described in this thread. With my phone heating up and not being able to see my photos I panicked and downgraded while I still could to iOS 12.
I’ve just been keeping an eye in the forums to see if these overheating and messages indexing bugs are fixed and it seems like it’s hit and miss. Some say everything is fine and some are still having the same issues.
A new issue I came across is that in iOS 13 within the info tab in a message where your photos do (for some) eventually show up, you can’t mass delete photos/attachments anymore in iOS 13 like you can in iOS 12!
discussions.apple.com
Another reason for me to stick with iOS 12 for longer. I have so many photos between a couple of my message threads. Like 500 or more for some and I like to be able to go through them and select a bunch at a time to delete. This is no longer possible with iOS 13! Only one at a time! Yikes. I hope they bring this functionality back with an update!