*. Gnome 3
The major difference is the Gnome 3 or will be at least. New features, faster loading times, new look n feel and other major changes in applications, etc Gnome team promise up with many things hope it works out for both of us.
*. Indic Typing Booster.
The idea is simple behind the app. As the name suggests, the more you use it, the more better it'll be predicting your typing "habits" thus making your typing experience more enjoyable by "predicting" things. It is 20% complete at this time.
*. GCC 4.6+ ->>>>
The GNU C Compiler or the shortly known GCC is one of the basic foundations of the Linux world. They'll be giving an update to the current 4.6 version as usual.
*. Libre Office.
Yes... everybody seems to moving in the direction of the Libre office "thanks" to Open-office current owners arrogance. If you don't know what Libre office is .. it is actually one of the old Open office based office suite which was kinda "Forgotten" some time ago but thanks to the Open-office it is again coming back to life.
*. Robotics Suite.
If you're a developer who's into robotic software development then the Fedora team has decided to include a full suite of robotic application suite. Heck ... after sometime you can even create your own robotic spin as well. Anyway I think it is an interesting move.
Although these are just a few to name which I found when browsing their 15th release page but if you're fond of reading then they have other information such as Xfce and systemd, python... a lot more interesting updates and info to read as well!.
Anyway the fedora core with the 15 version should be something really interesting since major changes such as Gnome 3, etc are few things that basically "defines" Fedora in my opinion.