When I took national, it was out of Midway. So, I can't answer the Ohare question. But it was a very good experience. I sprung for the extra $100 for the first class upgrade (I was on a freeroll through a satellite into a WSOP satellite).

Good food, good service, smooth flight. Carried on bags so that was not an issue. All in all, I will fly them again from my home airport of PHL when I need to.