I usually book a breakfast inclusive rate but if I am upgraded (as Gold) as I often am, I find myself eating breakfast in the lounge anyway as it is more convenient and I'm not used to eat that much for breakfast anyways.

If I eat the warm breakfast downstairs I may eat too much (which I regret even before leaving the breakfast table).

When on holiday this is different, though. Then I prefer a decent breakfast before a days sighseeing.