Has anyone tested CM6 with Unity and which version Unity will work? I heard a rumor that Unity 4.0(x) will not work with CM6, must be upgraded to 4.1 or 4.2.
The CallManager compatibility chart confirms your suspicions - http://www.cisco.com/en/US/customer/docs/voice_ip_comm/unity/compatibility/matrix/cutspmtx.html#wp51076
I have not tested CCM 6.X yet, but we are preparing to have Unity 5.X running before we upgrade CallManager to 6.1 or the next dot release in summer 2008 (hopefully). I would be interested in others thoughts as well or test results.