I have experienced warm rather than hot food on quite a few airlines...EK and QF being the last two that come to mind. It has always happened when seated in the premium cabins and never in economy for some reason.
I can eat almost anything and be reasonably happy but food which hasn't been heated up properly or has been left to go cold is my biggest bugbear when it comes to food onboard.

Do you get many requests from passengers to have their food heated up again?