We used to use it. But after a recent software update on the ground (EDYY and EDUU) we are currently not allowed to use it anymore as it apparently can disable the ground infrastructure. B737NG.
To be honest it had more of a novelty factor than real use and ATCOs often used voice comm instead as the canned CPDLC messages were not flexible enough for real world usage. Not to mention that it is much slower as well.