For me it tastes better warm, neither hot or cold.
Coffee is something quite special and is quite complexe on the tongue due to all it's flavor + taste on the tongue.
Theirs the bitterness that is decrease when the cup is hotter
The perception of sweetness that decreases when the cup cool, thus increasing the acidity
And their's the heat that is also a flavor enhancement (by making the flavor molecule more active)
Increasing acidity also enhance the flavor and balance the sweetness (think vinaigrette, splash of acid in a sweet sauce..)
I find it too acidic when it's cold and less complexe, and also when it's too hot your tongue tends to crisp up and you don't taste the flavor as much.