I've used ODIN to flash to my default ROM on a few occasions when my SGS decided to not boot. This is a sort of pain, since I flash back to stock 2.1, then I have to upgrade to Darky 8.0 on 2.2 to access the "Darky Configurator" and then flash again to the latest Darky after using the configurator application.
Are there default 2.2 roms available? I couldn't find any. If not, can you use Odin to flash to a custom rom like Darky's?