I've got the GA-P35-S3G, which so happens to be a very compatible board. Everything works, bar 5.1 audio.. Sound is however stereo and mic input works too.
From what I can tell one of the main differences between the GA-P35-DS3L and GA-P35-S3G is the audio, as the latter uses the ALC 662 chipset. Sound worked out of the box using the built in azalia drivers, but if you want your mic to work also this is no good. I used the following already compiled drivers, although the dump is also included in the package. They are afaik being developed for even better support..
FYI I've tried most DVD distros and the best one for the board is the Kalyway 10.5.2.
The best advice I can give you is to follow this EXCELLENT guide which worked fine for me, bar some minimal driver differences (audio). RLT1000 drivers are included in Kalyway but they are also included within the driver package in the following post. The Kalyway set-up is identical.
GFX card wise, I did have the ATi x1550 id 7147 but ce/qi was a tough bugger to get working.. so luckily I managed to exchange the card for an ASUS EN7300GT SILENT, 256 mb RAM, DDR2. Worked flawlessly and easily with a multitude of drivers - ATinject, NVKush, natit, NVinstaller v.52.. take you pick, this card takes em all without quibbles!!
I use a PS2 mouse / kb and needed the ACPIPS2Nub.kext installed after 10.5.3 (or was it .4?) went on, but this was a simple fix and I presume it applies to most PS2 set-ups.
I had some issues getting my TSSTcorp CDDVDW SH-S202J drive to write, but this (fingers crossed) turned out to be a drive firmware problem. I upgraded the firmware from SB01 to SB02 and it fried a few CDs and DVDs fine under OSX. Do a search for 'SH-S202J SB02' and you'll quickly enough find the firmware.
I am also having some issues with the USB2 hot-plugging in as much as the light on my SD => USB converter does not extinguish when I remove the device. It does on Windows. Other than that, it does work full speed.
At one point I could not get USB drives recognised unless I booted with the drive inserted.
Also, beware of the System.kext vs kernel version differences as I did not get USB devices working when these differed. These are all universal guidelines and are not limitations of the motherboard.
Any advice on USB hot-plugging would be very much welcome as this is the only thing giving me minor issues, but that could be attributed to me being a perfectionist!
As for getting Fusion (1.1.3) working on an MBR drive with a WinXP partition installed on the same drive and using a Darwin bootloader, it IS very much possible;
I did have to use my gray matter a bit as I did also get this problem;
Device could not be accessed exclusively.
A reboot will be needed for changes to take effect. OK? [n]
All I did was install chain0 on the XP partition, changed the active partition to XP and booted into OSX to get through steps 1 and 2.
Still having issues? DELETE THE BOOTCAMP CONFIG FILES in the Fusion settings folder, forcing Fusion to re-build them.
Once you get Fusion up and running, change the active partition back to OSX and remove chain0 from the WinXP partition. All will be back to normal and you will have Fusion working!
It really is stunning running full screen and using Spaces to flick from OSX to XP.. or the unity mode.. using F9 F10 F11 on windows apps is hilarious..
And both are on the same HD, on separate partitions. Take your pick at boot, or run XP within OSX. awesome!
finally, iMovie and iDVD 08 had a fit but that's their problem, so just software update them and all will be good.
so what's the score?
Kalyway 10.5.2 distro used, the rest gave me issues. Updated fine to 10.5.3 using the Kaly package, then software update to 10.5.4 via the net.
mobo: GA-P35-S3G, 2gb ram, sata HD, IDE afaik (haven't checked) DVDRW.
Core2Duo 2.2 CPU, both cores working
GFX card: ASUS EN7300GT SILENT, 256 mb RAM, DDR2
OSX 10.5.4, vanilla kernel works fine!
reboot, shut down, sleep works
ci / qe works with ease, no fiddling necessary
DVDR works (fingers crossed)
Audio works (2 channel + mic). Master adjustment of volume with ALC662 drivers not possible (but drivers are evolving). With built in Azaila drivers it is, but then your mic does not work.
That's it for now, any questions let me know.. I'm off to have a well deserved break!