When I was younger with an irregular schedule I could easily get by on no breakfast like most of you. Never a void coffee couldn't fill. But nowadays waking up early all during the week my body pretty much demands some kind of fuel to keep me till lunch. I go with the cold breakfast only because it's quicker. I save the hot breakfasts (all that bacon, pancakes, eggs and such) for the weekends when I have time to prepare/clean.
The biggest challenge I find is to keep it fresh by changing it up from time to time once you grow sick of it. There are only so many different types of granola to mix with plain yogurt, but I'm thinking my next favorite alternative would be bread + jam(s). Lots of different breads and jams to mix. Plus, it has the benefit of easily being served warm, and is filling and yet not heavy for an early meal.