for more info on CPDLC, goto...
http://usrwww.mpx.com.au/~cjr/CPDLC.htm
WRT, who uses CPDLC currently. I believe all B777 were delivered with FAN1A capability. Many 747 and airbues are also being retrofitted with such capabilities. I know MH, SQ, QF uses CPDLC regularly.
SR