What sorts of styles do you like? What are the sizes of the rooms containing the wood? If you like dramatic differences, then yes, paint it black or a deep rich color. I like red. Dark colors can make a larger room feel cozier, depending on the color. If you like light and airy spaces, go for lighter stains or colors (also good for making small spaces feel less closed in).

Personally, I love knotty pine. What's the point of having it if you don't show it off. Sand it down and seal it. If you have any pics, that would really be great. To be sure, we'd all like to see it.