In June 2009, we got United States v. Grant, 567 F.3d 776 (6th Cir. 2009), in which Judges Keith and Merritt concluded that once a Rule 35 motion is made the district court can consider all of the 3553(a) factors---not just substantial assistance---in departing downward. Judge Gibbons dissented.
The majority said that "[o]nce the grip of the mandatory minimum sentence is broken, the sentencing judge may consider Sec. 3553(a)."
Unfortunately, on October 16, 2009, the Circuit granted rehearing en banc, vacating the panel decision.
The case was reargued en banc on March 3, 2010. I'll try to keep you posted on the issue.