Yes, the health app. Medications was causing a black screen every other day first. I reported the widespread bug others had. Black screen now fixed (was not my phone was once again the software in the phone). Now it misses logged medications, I have reported this also. Maybe next year it will work? It seems to be syncing issues with iCloud as it is stored there.
Battery drain is real, are you not reading this thread, it is quite long and extensive?
Siri either stops from taking requests or takes requests and does nothing, restart only way to get her back. Widespread issue with software as it does not relate to just my phone, google and you will find.
RCS messages sometimes does not go through or gets massively delayed to my wife's phone when we are in a group chat with Android users, she has it set to on. She has iPhone 16 Pro Max, problem comes and goes. Can be network possibly, maybe it's not Apple.
Lagging and freezing can indeed be a local problem, but should be fixed regardless... Just because you do not see these problems they are not existing for the rest of the worlds iOS 18 users.
All I can say is that iOS18 is more buggy than iOS17, that is my perception of it. Obviously not yours.
I guess I am not alone: https://news.ycombinator.com/item?id=42291009