More integration and features for iCloud Keychain.
Fingerprint readers on Macs
3rd-party API
Multiple-monitor / Full-Screen is still a mess.
Needs more options so I can use it like it was (treating multiple monitors as one big screen) or like it is now (each separate).
And please get rid of (optionally) common menu-bar at top of screen. It's so out-of-date and requires way too much arm/finger movement on large monitors.
They probably won't change it since that would be like Windows (but probably not by the time they change it). Until then, just have to use things like menu-pop.
Calendar is getting better but it still can't select different time-zones for From: and To: times, which makes it a pain to enter flight departure and arrival times. Of course, I can do the math, but I shouldn't have to with a rMBP with a 2.5GHz i7! 3rd-party apps can do this, so Apple is just being difficult.
Contacts needs work. I don't care whether or not is has faux-leather binding. The damned thing still can't duplicate a contact!!! I'm often creating several contact for people at some company so most of the card is the same. I'm so tired of having to try the repeated info over and over again.
Maps. Great that it's finally here! Needs street-view. This is very useful when traveling to new places to see what I should be looking for as I drive.
Needs multi-destination directions.
Needs to be able to rotate. Don't always want North on top!
Need a lot more public transportation.
In other words, needs to do what Google Maps does!!!
Reminders - was this updated at all? It's too primitive. With a few more features, it would eliminate the need for 3rd-party task management for most people.
The "remind me at location" needs to allow multiple possibilities. I need to be able to say "remind me when I'm near a supermarket". It's almost useless the way it is since I'd have to explicitly have reminders for every possible market (bank, hardware store, etc) that I could possibly be near!
NewsStand: they've got iBooks, finally. Where's the magazine/newspaper app?
This also brings up the need for much better iCloud sharing of things like books, music, etc. It's totally absurd to think a family would buy multiple copies of the same book. There needs to be a way to share and/or loan items.
more later...
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Couple more I just remembered:
Single wallpaper for extended desktop.
Launchpad: can actually be really handy but it's too much work to set up. Why can't I select multiple icons and group them like finder and do with files? Nested folders?
Was this updated at all in 10.9? Kind-of dumb to ignore this since Apple is pushing the merger of iOS and OSX.