What hardware are you using? I looked briefly into this since I also have coax run throughout the house unused, but it was hard for me to know what to look for.
I'm running a MoCA 1.4 network at home with a mixed set of ActionTec ECB2500C and Netgear MCA1001 Ethernet-Coax bridges. The interoperated w/ no problems.
You can get newer versions that support MoCA 2.5, but I haven't tried them.