AMD says they'll have it fixed this quarter; they'll have to release a new AMD768 southbridge, since that's the component that's screwing USB. Once that happens, the board manufacturers will start using that southbridge's USB and stop shipping the freebie USB cards.
As for 64-bit slots, they can still be used for 32-bit cards. 64-bit, 33MHz slots are fully backwards compatible; 64-bit, 66MHz slots (the 760MPX's slots) are not. The critical factor is that 64-bit, 66MHz slots can only use 3.3V PCI cards (either 32-bit or 64-bit). The technical details of this are described <A HREF="http://www.anandtech.com/showdoc.html?i=1414&p=3" target="_new">here</A>.
Keep in mind that if you go sticking a 33MHz PCI card in one of the 760MPX's 66MHz slots, you'll cut the link bandwidth between Northbridge and Southbridge by half.
Your other option is to go with a Tyan Tiger 760MPX board, which IIRC has six PCI slots vs. the five on the Asus. Or, since you're not that concerned about 64-bit PCI, you could use a Tiger 760MP board, which is fully backwards-compatible with 32-bit PCI.
I kind of know how you feel on this point; the "freebie" USB card is kind of an unclean solution, especially when a real fix is coming down the pipes so soon.
<i>If a server crashes in a server farm and no one pings it, does it still cost four figures to fix?