This was touched on in the 8.41 sticky thread, but I never got my head quite around it.
I gather there is significant crossover in the functionality of these two? Is there anything missing that DDM doesn't have or vice-versa?
The reason I ask is that DDM functionality would be much more useful if it had full integration with distros and desktop environments. RandR support seems to me to be the only way that this is likely to happen. Is adapting DDM to RandR simply a matter of adding a different API to the same functionality, or is there a ways to go for fglrx yet? Have AMD hinted at or made any announcement about RandR support?
I have no real experience with ATI's DDM. Basically ATI and Nvidia have respectively DDM and DynamicTwinview. Both allow you to configure your displays, resolution and so on while in X. I'm not 100% sure about ATI but Nvidia for instance didn't handle rotations of displays with DynamicTwinview.
Anyway RandR 1.2 is basically a generic way for doing DDM/DynamicTwinview. It is more or less the same (though RandR allows proper rotation and some more stuff). It is natural for ATI/Nvidia to move over to RandR 1.2. Nvidia for instance layers RandR 1.2 on top of their DynamicTwinview, ATI will likely do the same. It is nice to have this a standard finally.