CPDLC is still in its infancy to where it wants and needs to be to become a game changer.
We do not (yet) use it, but transit several provider sectors. My previous airline was already equipped.
Ultimately the CPDLC aim is (but not limited) to:
- reduce radio congestion on the old VHF;
- reduce dialect issues requiring rereading clearances due lack of understandability;
- enable more direct routings to be given and acknowledged to crew;
- enable vertical clearances/restriction to be given and acknowledged to crew;
- enable a more flexible use of airspace for all involved;
- ... the list goes on.
Personally, I can't wait until CPDLC is implemented properly, like several other EuroControl projects out there at present which can, and if implemented correctly by an airline, will make a huge financial and time saving.