My new one lasts 2x as long before charging and I can take beautiful photos that aren't grainy at all like the last one. Its absolutely worth the cost for me!
It really depends on the type of upgrade. Of course if you have a really old phone it may be worth upgrading, but keeping up with the latest is a waste of money and energy.
True. I only truly got rid of mine because I was on the 2nd screen and 3rd battery, and I was tired of having to charge it so often.