The only bright note in the opinion is the Government's concession that once a defendant satisfies the safety valve, the district court should treat the Guidelines as advisory in light of Booker. Though this contradicts the plain language of Section 3553(f) (district court "shall impose" a sentence "pursuant to" the Guidelines if defendant qualifies for safety valve), and though Booker itself did not "excise" this provision, the Government conceded that this provision "should be interpreted to mean that a district court [need only] 'consider' the Guidelines in an advisory fashion" once the mandatory minimum is no longer, er, mandatory. Op. 3-4.
The Court did not ultimately reach this issue since Holguin failed to qualify for the safety valve. However, the opinion strongly suggests that the Court agrees with the Government on this issue and that once a defendant satisfies the conditions for safety-valve relief, the district court should consider the Guidelines as only advisory in imposing sentence. Op. 6.
UPDATE: Professor Berman has once again beaten us to the punch in our own backyard (early morning mixed metaphor) -- click here for his discussion of the case (which mentions the opinion's use of an odd neologism -- "a condition of the guilt of the crime" -- for the far simpler term "element").