Consistency in dereferencing is very important. empty() should at some point be deprecated, but fixing this erratic behavior for now is good imo.

The default value for method arguments is a shockingly bad idea for a new feature, it only supports the old, bashed upon, code quality that have been PHPs greatest legacy problem. If anything in this alley I'd like to see named arguments somehow.

I'm not so sure about property getter/setters as I find the syntax a bit awkward, all while magic methods lets you create getter/setter based APIs.