it has been a long time since i actually had to render stuff. that was rhino4 i think with vray-for-rhino 1 or 1.5. i also do remember, that setting the right tile size was very important.
it seems, that proper openCL/AMD support is on the horizon, we are just not quite there jet.
@nathanletwory
btw, i hope we will see the cycles commands also to be available in a dedicated sidebar and the settings should be remembered/saved with the file.