I have 10.5.7 running on my EeePC 1000HE.
Things actually work better with 10.5.7, no more need for the cpus=1 option, the OS now recognizes a single CPU with hyperthreading, CHUD's CPU preference pane shows the CPU as "Intel Ultra Mobile Processor" and allows selective enabling/disabling of hyperthreading.
Only the new GMA950 related plugin and bundles need to be rescued over from 10.5.6, because the new ones don't properly jive with the hacked GMA950 and AppleIntelIntegratedFramebuffer kexts that are needed for the video resolution to be properly recognized.
Otherwise, 10.5.7 requires the same additional kexts and same kext overrides as 10.5.6.
An I'm not running iDeneb or something like this, but an almost vanilla install with Chameleon 2.0RC1 on an HFS+ formatted EFI partition on a GUID formatted drive.
Dual booting into WinXP also works. What didn't work was transferring the original WinXP with WinClone. So I had to install WinXP from scratch for reasons that are beyond me.