The first release candidate of PHP 5.4 was just released. The announcement on the main page is still missing, but the links are the usual ones:

If you haven tried out traits in PHP yet, please do so now. We have fixed 19 issues so far, but there are probably still a few corner cases we have not yet covered.

In case you find quirks or bugs, please report them either on the bug tracker, on the internals mailing list, or directly to me.