That depends on who you ask and the reasoning for the upgrade. I was about to give a run down of everything it has to offer but it's really common knowledge as to what to expect. But in brief, here's my short of it:
-Bigger, brighter, more responsive screen and refresh
-Longer battery life
-More powerful device in every aspect (Graphics, CPU, RAM, ROM etc)
-Greater camera variety for more occasions
The cons are of course:
-No micro sd slot
-No headphone jack
-No HR sensor or IR blaster
If you feel dissuaded by any of the cons then it is entirely up to you to determine whether to make the compromise, so ultimately the choice lies with you and whether you feel you need it or not.