10.5.2 "worked out of the box" for me. The only (minor) issues I had were the ALCInject.kext not loading correctly on the first run - but I fixed that swiftly with a quick permission repair. The nForce 5 Lan is still a no go, but that is now somewhat irrelevant to me since I have a cheap PCI NIC that works perfectly. The GUID boot loader needed fixing - that can be found
here.
So far its been
very stable, extremely fast and working as a real Mac would.
OS X: Leopard 10.5.2 EFI+GUID
Board: MSI K9N SLI nForce 570
CPU: AMD Athlon 64 X2 6000+
RAM: 2GB Corsair Value 667 DDRII
Graphic: XpertVision NVIDIA GeForce 8600GTS 256MB
HD: Samsung 300GB SATA-2
Optical drive: IDE Sony DVD RW DW-Q28A
Sound: Onboard 3 Port Realtek ALC888
Apple Pro Keyboard
MS Optical IntelliMouse Explorer
LG Flatron 20" Widescreen LDC @ 1680x1050
/me is very happy