The first major update says that Niantic has "made improvements to the accuracy of a curveball throw." Along with Pokémon being harder to catch, the curveball being more difficult to throw was a major complaint coming out of the last update.
Niantic's update says that there was a "bug" preventing "'Nice,' 'Great,' and 'Excellent' Poké Ball throws from awarding the appropriate experience bonuses." That bug is fixed. Get your Bert Blyleven on.
You know how you thought of that hilarious nickname the day after you named your avatar "Pizza Tuesdays 4Eva"? You can fix that now. The updated has "enabled the ability for Trainers to change their nickname one time." You're only getting one shot at the name change, though. Better make it real clever.