I don't love cold couscous, although I find it satisfying enough if it's allowed to get to room temperature (I assume we're talking about leftovers, here). That's true with other pasta salads, too.
With grains like quinoa or barley or, my very favorite grain for salads, farro, I actually like to warm everything up a little bit before I eat it. The grains dry out more quickly than the pastas, and I find dried-out grains really unpleasant. Honestly, I like all my pasta- or grain-based salads a little warm.
I won't go near a cold rice salad (again, I'm talking about leftovers -- I can totally deal with cooled rice that was just-cooked). In fact, rice-based salads is the one thing that I can't handle as a leftover at all. I have to fry it.