I have a guy who dislikes swimming, but when I put him in the pool, he swims anyway. Is this a bug or on purpose?

Probably an oversight. We'll see about fixing that one up for you, Jazzo!

Perfect.

I have a kid who dislikes music but by golly, he's always by the MP3 player dancing...maybe a closet musician???

It seems to me like the likes and dislikes are not as strong as they were in VV3. For example, I had one character who disliked sunlight and yet had no problem going out in the daytime... she didn't immediately run back inside or something if she was taken out. She may not have gone outside in the daytime spontaneously as much as others might, but that would be a variation that would be hard to confirm. IIRC, in VV3 the dislikes were more likely to cause refusing to do something or running away from something.