There are several considerations.
The new idea is that you are in a constant descent rather than a stairstep approach where you hold at maybe 20K feet for a while, then drop to and hold 15k for a while and so on.
Of course, the terrain is a big factor here, it has to cooperate because you don't want to hit it.
A debate has been going on for a while about whether it is bad to "shock cool" the engine. The idea is that you might damage the engine by cooling it too fast by just cutting it off to descend. Some people say this is a myth, some say it is real. It probably depends on the airplane and the conditions at the time.
For any approach it is important to be stabilized. Certainly on Final Approach we always taught that you want a constant speed with a constant descent rate on the glidepath.
In the real world you can try to do this, but to some extent you are at the mercy of the guy in front of you. If he is slowing down and speeding up you have to compensate. Wind is another factor that will cause you to make adjustments and those adjustments will cause everyone behind you to compensate.
I guess it could help with large airline planes. If they can get everyone sequenced together and stabilized it could work, it might take a while to figure out exactly how to do it.
