What's so difficult about VNAV PTH descend anyway, just fill in the bits and bobs on the forecast page and you won't be far off!
The Descend option is nice but really is no solution, it only goes into a 1000FPM RoD to capture the Idle Thrust Descent path after crossing your normal T/D point..
The only reason I can think of is by lowering stress on the engines after a long cruise by going down a 1000 FPM before Idling it out.....
3 x Track Miles to go plus some miles to get the speed off works very well, and speedbrakes can be very effective but you have to have high speed...........