A friend of mine complained about restaurants she visited on a trip to Europe. 'The food is never hot, not even the soups,' she said. By 'hot', she meant blazing hot - the hot you get in Chinese restaurants, where stir-fried food is scooped from a wok and rushed straight to a table.
While I agree that some dishes are best served 'hot hot hot' - because tepid chow fun is a soggy, heavy mess - I actually like some dishes when they've had a chance to cool down a bit. It's not just that you risk burning your tongue on very hot dishes, but because you get the true flavour of the food.
Extreme temperatures, whether hot or cold, mute the flavours of food and drinks. It's easy to test this: take a sip of white wine that's been chilled in a normal fridge (rather than one reserved for wine) and it will hardly taste of anything; warm it slightly in the glass and the subtleties will be revealed. Serve ice cream when it's so hard that you need to warm the spoon to scoop it from the container, and it's not nearly as good as after it's had a few minutes to soften slightly. At the other extreme, try drinking soup when it's so hot that a sip of it scalds your lips and tongue and you can't really taste the flavours as well as if you had allowed it to cool slightly.
In no way am I suggesting that all food be served tepid - that would be dull, because temperature contrasts on a plate of food can be just as interesting as textural contrasts. But if you're making something that's meant to be eaten either very hot or very cold, be sure to taste it just before serving, to make sure there's enough seasoning - you'll probably need to add more. Very fatty foods, such as braised pork belly, taste better when very hot because the fat is more melted than when served just warm, which lets the fat solidify. To perk up the flavours, hot, fatty food is frequently paired with sharp condiments, such as pickled vegetables, mustard and vinegary salads. And when I make a batch of ice cream or sorbet, I taste the mixture at room temperature and make sure it's quite strong, to compensate for the muting of the flavour that will occur when the ice cream or sorbet is frozen.