I use two MC2=Zen (one S/PDIF and one AES-EBU) in my setup. Very happy with both. I've tried some other good digital cables including Pure Note, Nordost, Argent, Tara Labs, and VH Audio. I did not find great differences among most of these, and the MC2 remain in my system.
The only non-AZ digital cable in my setup is a S/PDIF VH Audio Pulsar with Silver Nexgen connectors. I use it between the transport and RCS 2.2X. Great cable with a very similar sound to the S/PDIF MC2.
A friend has recommended the Cerious Tech digital cables but I have not had the chance to try them yet.