Catalyst does not support hybrid cards (PowerX) yet. And as far as i understood from the thread "Catalyst with Intel IGP" there are still no plans for this
Yes, it's true. You're also out of luck if you use proprietary nVidia driver + Intel IGP too (Netbooks with ION2 platforms, for instance). I still believe this is more a kernel / Xorg design problem than a driver one, but that's an answer that only Xorg/Kernel/ATI/nVidia devs can tell us.

who cares?
A lot of people care about it. Currently, there are lots of computer systems (mainly laptops) which use a hybrid graphics solution (discrete + IGP). And Linux only works ATM (with some problems) with OS drivers. Because OS drivers have a very slow 3D performance, most people who have hybrid graphics solution and want to use 3D features have no other solution than install / dual booting with Windows.

Cheers