1.*iPad-like gesture app switching.
2. Gestures in Safari.
3. "Official" side menu.
4. Scrollable Folders.
5. Ability to hide stock apps.
6.*Ability to choose default apps.
7. Wallpaper slideshow.
8. "Quick Response" interface for SMS/chat apps.
9.*Photo Booth for iPhone.
10.*API for game*controls.
11.*Live Icons.
12.*Keyboard and Mouse Support (Including app shortcuts).
13.*Free icon layout on home screen.
14.*Air Drop.
15.*Facebook-style photo/video viewer.
16.*Browser file uploading.
17.*Themes.
18.*Search for contact conversation in Messages.
19.*Ability to record the screen.
20.*Ability to copy text within a text message, rather then having to copy the whole message.
21.*Combine Maps & Compass.
22.*Ability to view message details for every single message.
23.*Move iPad Notification Center to right side of screen.
24. Improved DND.
A good comprehensive list with nothing too tacky in there. Better than the ability to assign garish colour themes to things!
I'll add a couple of my own here:
* Improved navigation options and displays
Things like an automatic night colour scheme - when it comes to sunset, the bright background on Maps Navigation fades to a black background with grey roads and dims the brightness.
Speed camera location database (or the ability to import third party POI databases - speed cameras, restaurants etc).
Strike a deal with Google for use of their POI data?
* Unified cross app file system
Not a file system as such, but the ability to attach a file to an email that you have stored in a certain app, but from the Mail app itself. E.g. double tap your email, attach file, select an app, then see the files stored inside that app.
* Swipe to change tracks
Similar to the spotify app - allow the user to swipe right to skip track, left to previous track - ideal for in car. Also on lockscreen!
* Location based phone settings
You can customise what settings are enabled in what area. (home, wifi on, BT off, for example).