Originally Posted by k0nr4d

It really depends on how you coded. There are behavioral changes that break code, needlessly. The biggest thing that pisses me off specifically, is that you can no longer do:

if($var) { ... }

Before, if $var was not set at all it was just false and didn't enter that. Worked for years and years. Now, that would throw a fatal error. You now have to do:

if(isset($var) && $var == true) { ... }

So it introduces alot of fatal errors where it wouldn't throw them before.