As a veteran of hundreds of climbs and decents of the Pali (with a dic equipped bike), I can wholeheartedly agree with this post.
On my disc equipped MTB bike, I routinely hit 40->45MPH on decents either town bound (Honolulu) or Kailua bound. Kailua bound is also more 'fun' as there is a 180 degree turn at the 3/4 mile point in a particularly fast part of the descent. It is also sometimes wet from rain.
If you go on an off-hour time and take your time, the ride is nice, especially using the old Pali road sections..