Some interesting stuff from the FDR & aircraft performance reports for those who can't access them right now:

They were level at 2400 before the decay in speed began.
Power levers went to flight idle when landing gear was deployed and never increased until after the upset.
Speed began decaying upon gear extension and was never arrested.
The captain called for Flaps 15 & landing check when the plane was already almost to the Flaps 15 vref speed. The flap handle had just been moved when the stick shaker went on, they were at 6.7 degrees (had been at 5).
Stick shaker went on at 126 knots. Calculated 1g stall speed in their configuration was 107 knots; at 126 knots it's calculated that 1.38g would stall the airplane.
Following stick shaker and autopilot disconnect, strong nose-up force is detected on the captain's yoke. The aircraft achieved 1.42g and a pitch and angle of attack of 20 degrees before stalling.
During most of the upset, the speed was between 90 and 110 knots.
The first officer appears to have retracted the flaps during the upset without prompting, as though for a go-around.