Hey Nic,
So I've had my evil fingers in some of the implementations and primarily in the OpenStack implementation. The OpenStack Implementation is complete and OCCI 1.1 compliant. There is another OCCI implementation on OpenNebula and this too I know is 1.1 compliant. CompatibleOne is also compliant as is pyssf, pyOCNI, tuOCCI [1], and occi-py [2]. The useful thing is the DYSO app that performs OCCI compliance testing for new and existing implementations. More fuzzily (my knowldge), WNoDeS is OCCI compliant and is also is used within CERN, though I might have my wires crossed there.