They were discontinued in the new calendar which is a great shame.
Since 1972, the Cycle of Prayer, set by the Bishops Conference, has sort to fill the void.
My personal experience is that this cycle is not the subject of much promotion at parish level, often only a footnote in a newsletter to remind the faithful they ought to be praying!
Not so with Ember or Rogation days as they are fixed in the calendar, with bespoke liturgy in both the Mass and the Breviary.
I have blogged before about Ember days here and here. However, an even better commentary has been reposted over at Rorate Caeli and I would encourage you to read it.