Imagine a buffet breakfast at WDW that has no characters and you don't have to pay for at the end. Now you know how it works. You go down for breakfast, eat, leave. At some ES's they will give you vouchers for each registered person in your room, and the hostess will colect them as you are your way in. I can't remember how that particular hotel works it. (There are no assigned seats, you grab which ever table you'd like.)
Not much. If I recall draft beer and soda, and maybe some cheap-o wine, and popcorn. It's not something you can even try to make a light dinner out of.
ES breakfasts are quite good. They usuallly have an omelette/egg station, manned by a chef, in addition to the "obvious" full breakfast buffet. I don't seem to have a good excuse to stay at them often for business, but when I do I'm really happy about it.