On the MacRumors Forum you can see a large list of hidden characteristics on the new OS, here you can see some of them.
Previously, if you launched the Notes App and you had no notes saved, the app would automatically open a new note and the keyboard would pop up. It no longer does that. If you have no saved note, it just says No Notes. (found by cypriote)
In Maps, directions are smoother. The next direction slides in nicely and has the distance to the next action PLUS that action on the same screen, as shown below. Previously it would’ve said on action 6 “Drive 63.3 Miles”…action 7, “Continue on I-91 N….” (found by Marvin1379)
Playlists starting with spaces and/or dashes no longer appear at the top of the list in Music. (found by agentkow)
Any favorites you may have in the old YouTube app can be merged into your YouTube account when you sign in to the new YouTube app. (found by agentkow)
For Exchange the old “Passcode Lock” feature (required by some IT departments) had delay times of up to 15 minutes where you would not need your password to get to your phone. There is now a 1-Hour option and a message about longer times being less secure. (found by CinciJeff)
When you enter safari and you reconnect to wifi the screen grays out and says “Connecting…” (found by ChrisWilder07)
You can now download apps redeemed from promo codes on the device. previously you could only redeem them and had to download them in iTunes
If you had a Safari Bookmark on the home screen, and the website didn’t have it’s own icon when you made the bookmark, if the website ever does get an icon, it will auto update on the home screen (found by iPhone Chicago)
In Stocks if you “swipe” the mini-graph left, then a more detailed stock quote will show up with Open/High/Low/Volume/PE/Mkt Cap/52w High/52w Low/Avg Volume/Yield…and if you swipe another time to the left then news for that stock comes up and the news is scrollable in the vertical direction. (found by iPhone Chicago)
When exiting an app, the minimize effect now has shading to make it seem more like it’s disappearing into the distance. (found by Cousin Dirk)
If you want to see the rest of the list go here .