I also was able to install the combo update from 10.8.2 and restarted without modifying any kexts and it worked fine. However, my audio (ALC662) stopped working and the updated 10.8.3 modified kext for it did not recover my sound. So I just decided to do a clean install with my updated unibeast USB stick, and now everything is working again (video and sound). Again, did not have to modify kext as you pointed out for my GT610.