Update went smoothly here
P5K Premium WiFi w/ Q6600
Kalyway 10.5.1 > 10.5.2 > 10.5.3 > 10.5.4
XFX 8600GT 512MB RAM (w/ NVInstaller v.52)
Downloaded 10.5.5 Update (not combo) from Apple, and installed using netkas' instructions, didn't need to modify the InstallAtStartup script. Restarted (plain restart, no F8, no -v, and no -f).
Everything seems to work perfectly, didn't need to reinstall any kexts. Video still works with QE/CI. Audio still works.
Also tried the same exact procedure on a iDeneb 10.5.4 installation (installed on an iPod) and it went fine as well.
Hope it helps.