There are a couple things I don't agree with. Like adding goto statements. Really? Come on...PHP...
But it seems PHP6 wants to finally remove old deprecated behavior (registered globals/magic quotes/safe mode) which I think is a good thing.
Not to mention namespaces will be a great addition to the language.
At first I had an issue upgrading to PHP5. It didn't have the same speed boost PHP3->PHP4 had, so I didn't see the need to change.
But then I actually looked into the new features.
The OOP improvements, exceptions, SimpleXML and iterator support are all great features I use daily and wouldn't want to move back to PHP4.