Scalia is correct that the appellate review provisions will wreak havoc, but that havoc is a byproduct of Congress scoring political points at the expense of judicial discretion. I have never been comfortable with mandated sentences. IMHO Congress would better exercise its authority by careful review of judicial appointments. If the candidate cannot be trusted to exercize a reasonable weighting of the specifics of each case, the candidate does not belong on the bench.
Life is not always fair, but that is no excuse for setting rules which guarantee unjust sentences with no consideration of mitigating factors allowed, a process which institutionalizes gross injustice. If we are to appoint persons as judges, we should allow them the latitude to actually "judge" all the factors admissable in individual cases.
I find the holding that thousands of individuals should serve sentences far beyond the merits of their particular circumstance merely for the convenience of the judiciary system to be a travesty inconsistent with the alleged concern for the rights of the people our country is supposed to stand for.
The way I read this opinion is that Scalia(Thomas/Stevens) want a JURY to determine the FACTS (drug amount, culpability as mastermind of conspiracy, etc.) that will blow the defendant away, not JUDGES.
The problem is Ginsberg who switched sides on the remedy, and made the guidelines advisory.
The easy (and constitutional) solution was to place the facts in front of a jury, and keep the guidelines mandatory.