The diffraction thing is just something to point out when people are looking for the ultra sharp sweet spot, vs mastering the depth of field, and the gray areas between... Mostly for the pixel peepers that try to compare an upsized 12mp full frame image to a 24mp crop sensor to a 24mp full frame with three different lenses, subjects, and lighting conditions... ;)
Basically, hey, this is a new camera. Learn it before you judge it...
Anyway, I'm pretty excited about the new Sony gear, but in a way that makes me want to go out and use what I have more than ever... No matter how awesome the new tech is, it's not likely to make me any better at "seeing" and "capturing" my next awesome photo... That, I need to go out and do myself....
As for the 24mp RAW being the only option, that may be the case... That would be a definite bummer. Just double checked my a900, and yah, as soon as you hit raw it locks it at "Large" image size... Oh well...