Hi.
Recently I replaced my iPhone 8 battery and, after that, I made a clean install of iOS 15.3. Until then I was on 14.4.2, so this is my personal experience with iOS 15.3 after a week.
The phone is snappy, memory management is good. Compared with 14.4.2, I’d say is better, considering this device only has 2GB of RAM. Everything works. Calls, 4G, WiFi, Bluetooth… and with the great features of iOS 15 like the tab groups working like a charm across all my devices.
I’m very happy with iOS 15.3 and battery life is great (between 7 and 8 hours of screen on time, which is awesome for a device with only 1.821mAh) but considering I just replaced my aged battery, it’s not a surprise. Keep in mind, though, that iAppleBytes YouTube channel battery test shows that iOS 15.3 is one of the versions with worst battery life. Maybe it is because my battery is new, or because I performed a clean install restoring my device as new and not using any sort of backup, but my experience is different, and I am pretty happy with the battery performance on 15.3. (EDIT: screenshots attached, 8h using mostly Safari and Discord)
However, there are two minor issues. It’s not something important enough to not stay updated, but I feel obliged to share them: lag on the first Control Center summoning, and lag switching on the flashlight. It’s like less than half a second, maybe 0,4 seconds, but it is there. Keyboard is at times -just every now and then- slightly sluggish, but it is not something that interferes with my usage.
Other than that, I’m really happy with iOS 15.3 and, at least on my iPhone, I’ll stay here for a long, long time.
If you need me to test something in particular with my iPhone 8, as long as it doesn’t involve downloading anything, just let me know.