Pre-cum, yes when masturbating, no during sex. The taste is legitimately pleasant (like lightly buttered popcorn) and it turns me on in addition to just tasting good.
As for cum, not usually. The taste is less pleasant (closer to black pepper). The idea of doing it is arousing while masturbating, but once I actually cum, my arousal level dies off and it becomes a much less appealing prospect.
The few times I've done it, it was at the behest of a female partner and it was a turn on for them (having me go down on her right after I came inside her, kissing after a blow job while it's still in her mouth, etc).