I've seen a WHOLE LOT of destruction from hurricane Gustav in the past few days. It usually is oak tree versus framed house or oak tree versus stick roof. The oak tree usually wins and wins big. How would a SIPS roof hold up?

That depends on the size of the oak tree.
But overall, the SIPS roof should stand a much better chance of surviving.

Jelly;

2 months ago a 30" x 60 ft. tall china berry tree fell on my own office, besides a little shingle damage & a small dent, the roof structurally was unaffected.
Several years ago I inspected a steel SIP house in Gonzales, LA. where a large oak fell on the house. The force of the tree popped roof about a 1/2" off at the top of the wall, but the only corrective measures needed was to install 4 new roof screws to draw the panel back in place.
I think the reason sips work so well in hurricane impact testing, is the skin & solid core absorb and spread out the shock of the object impacting the panel.
In the 2 instances above the tree would have gone right thru a conventional roof deck, but in both cases water did not even come thru the damaged areas.