In a new post to his site Benjamin Eberlei shares an opinion about traits, noting that they're basically the same as static functionality when it comes to several things like coupling, not being testable and being a "global state" container.

I used to look forward to traits as a feature in PHP 5.4, but after discussions with Kore I came to the conclusion that traits are nothing else than static access in disguise. They actually lead to the exact same code smells. Familiar with the outcome of too much static use, we should reject traits as just another way of statically coupling your code to other classes.

He includes some code examples showing traits in use in an example controller to handle a simple redirect. He points out at least six different issues with just this simple implementation. He rewrites it as "static" code to help prove his point. He comes to the conclusion that, much like static methods, traits should be avoided and instead aggregation should be favored.