1) Speed/Perf improvement on iPad. How come an iPhone 5C is fast and fluid but an iPad 4 is barely usable? They have the same guts. I've almost stopped using my iPad 4 since iOS 8. I've gone back to my Macbook Air. They transformed my 500, buttery-smooth piece of technology into a paperweight.
2) Better memory management. Kill badly coded apps that suck up the battery in the background. Kill them.
3) Don't send me 3 error messages (1 for Gmail, 1 for Exchange, 1 for iCloud) when I'm using mail.app and I lose connectivity. It's utterly annoying. Also, even when you'll give me 1 error message - don't force me to acknowledge it by tapping OK.
4) How about fixing orientation bugs in iPhone 6 for mail and messages? No, 8.1.3 here and it's still there.
5) Give me an option to opt out of auto full screen in Safari. I want to be able to switch tabs, go back and or open a new one in one tap, at all times.
6) Fix the Appstore bug on the iPad. i.e. I downloaded Tinder on the iPad a year ago, by searching for it and dl-ing it from the app page. Since then, the search field of the app store is always prepopulated with "Tinder" whereas I've been searching for and downloading dozens of apps since then.
7) allow to display 16:9 iPhone apps at 1x on the iPad retina. It's sad to use an iPad Air 2 as a blown up iPhone 4S.
8) bring back the iOS6 clock app. Alarms clock on my iPhone 6 drive me crazy, I can't turn them off easily in the morning when I'm sleepy and grumpy and they shout during my shower, annoying my housemates. My 3GS on iOS6 was way better.
9) give an option to set the quality of voice messages (in the messages.app) to a higher level i.e. voice memo quality.
10) give me an option to directly open documents from an email into an MS Office app. The powerpoint preview is useless in mail.app.
11) let me sort wi-fi networks in order of preference like on the Mac.