Got my beautiful XPERIA Z3 compact a couple of days ago and was instantly very annoyed at the completely useless What’s New -app, since it was integrated even in the launcher of all places.. Here’s how to remove it without root, idea from talk.sonymobile.com: Get-rid-of-What-s-New

root@Basecamp-Debian:/home/filip# adb shell
shell@D5803:/ $ pm block com.sonymobile.advancedwidget.entrance                
Package com.sonymobile.advancedwidget.entrance new blocked state: true
shell@D5803:/ $ exit

To unblock the app run

pm unblock com.sonymobile.advancedwidget.entrance

Edit: on lollipop replace block with hide!