It's a shame that developers are not developing for PHP 5 STILL! There is far more you can do with PHP 5 in terms of the OOP side of the card, and unless people begin switching sometime soon, and shed their fears of compatibility for a 2+ year old version, then just perhaps they'll find themselves inadequately learned when they finally do.
I've been moving onto using ZF recently as well. The first framework I used was CakePHP, but I grew tired very quickly of its low cohesion and strong coupling. I just adore the way you can pop out bits of ZF and use them independently of one another.