Should we celebrate Booker‘s fourth birthday?

After a day on the road, I return to e-mail with a friendly reminder from a friendly reader that four years ago today the Supreme Court handed down Booker and converted the federal sentencing guidelines from mandates to advice.  This same reader also sent along these questions:

Four years on, Professor Berman, and how “effectively advisory” are those guidelines?

How healthy is that Sixth Amendment jury buffer?