In my experience, the managed descent profile on the A320 is too conservative. It arrives at IAF-altitude too early, meaning too much before IAF, and calculates typically with a speed of only ~145kt at IAF instead of 185kt (which is what you typically fly at IAF: CONF 1, ready to set CONF 2).
To fly a more efficient descent, you basically have to use OPEN DES to start descent behind the TOD of the managed descent profile, which means you loose the function of the speed bug bracket of managed DES (variations of wind compensated with variations of descent speed), which is a pity.
So an optimized, more realistic descent profile calculation seems a good thing to me.