Okay here is my testing experience:
I took an empty harddrive and did a fresh install of Snow Leopard + applied the 10.6.6 Combo Updater - installed PC_EFI 10.6, added just the Kernel + NForceATA, fakesmc, SleepEnabler, patched AppleHDA + added Device ID for my HD4650 - everything else left untouched.
I could not boot without -force64 - all Kernels since Darwin 10.5.0 have this issue for me - without it fsck just shuts down my system. Darwin 10.4.0 and earlier works - independend from the applied patches.
This issue is not related to this realease, but am I the only one?! Can this be fixed?
First issue: The Systemassistant (that App showing the nice video and guiding you through the basic system adjustments) ain't loading - just stuck on grey screen with moveable cursor - this problem is present in any Kernel Patch since this one:
http://osx86.co/f36/10-3-0-qoopz-anv-kernel-rel3-t6450/
It is present independ from using Kernel dyld, Vanilla dyld or dyld with bin-patched sysenter traps.
If you are using the Kernel for inital setups like mine, this
sucks badly! 
Deleting sound and video file of the welcome vid doesn't solve this - neither booting with out graphic drivers (including framebuffer).
After beeing done with that, I installed upx via MacPorts and used it to pack /System/Library/CoreServices/pbs
Kernel related issues:
- SystemUISever doesn't work. The menubar icons including clock and spotlight are just flickering up sometimes but are not present the most time nor usable. Packing it with upx ain't possible cause of NotCompressibleException error.
Is this maybe related to binary decryption?
- all those kernel debug messages are nasty (all those segment fails - those messages are still appearing in dmesg after "DSMOS has arrived")
- Finder is crashing a lot
- System-Profiler is crashing
- system is beachnballing a lot, but this can be related to the first point
laudation:
- CPUID-autopatching seems to work - iTunes settings are working with untouched Carbon framework.
- 32-Bit Apps are fine within -force64 mode