Quick fact: RD580 development took 8 months from initial development to final product.

Motherboards

ASUS were the first to have motherboards ready. They even started selling before the official launch. Some lucky users are already playing with their boards.


All other major ATI motherboard partners will offer RD580 based solutions. Most of them will launch the boards at Cebit this month. Most boards will be very close to their RD480 counterparts so you will profit from the mature BIOSes that will have a lot of less initial issues.

Soutbridge

At this time there is no new Southbridge available from ATI. Manufacturers are free to use either ULi 1575 or ATI SB450 for their motherboards.
There is still plenty of talk going on about SB450's USB performance. Also there is a lack of SATA-II on the chipset. Regarding USB performance ATI had to say this:
"As for USB performance, go around your office and ask everyone to put all of their USB keys, USB mice and USB keyboards in a box, then test them all on SB450 and any nVidia, ULi or Intel southbridge. Do you see a difference?"
I completely agree with this. The only scenario where you can measure a difference is when you backup data to an external USB HDD. Since this is usually a sort of backup it does not really matter if it takes a bit longer. Just go have a coffee with that cute colleague of yours.