The Cayman cards use PowerTune (rather than PowerPlay) like the HD7000 series cards. I suppose the power tables are there for backwards compatibility.
I guess that explains it.
Mr Duecher has now gone off on a bit of a tangent with this bug, throwing out the safe profiles and messing about with the clocks and voltages independently. Not really interested in trashing my card, so I'm off to catalyst again. Good luck all.
Having done some more reading on PowerTune it seems it is not as different to PowerPlay as I first thought.
Basically it uses the same power tables as before, it is just that when in the highest power state the card hardware can automatically start to lower the engine clock when reaching the thermal limit, rather than jumping all the way back down to the next lowest power state from the table. This keeps performance higher and also allows the highest power state to have a higher engine clock value.
Newer HD7000 cards have introduced a boost feature, this is a new power state (with higher engine clock and voltage) that can be used temporarily.
You won't get anything as sophisticated as that, not as long as AMD have guys controlling the open source driver. The code is horrible, and based on what I've seen, that's intentional. The alternative is sheer incompetence.