I've had great success with water in the eggs. Got it off the old 'Frugal Gourmet' show. Milk actually doesn't work as well in my experience. That's not to say cheese or other dairy products can't be used in an omlette - just not in the basic raw egg mixture.

Messr. Smith also noted that Peanut oil worked best for cooking, as it could go to a higher temperature without scorching and left a better flavor than most other oils or sprays.

M