I agree with smittie that a tucked-in top with high-waisted pants tend to make your bottom look long and flat, especially if the pants are snug. This seems to be less of a problem with high-waisted but loose trousers. The look I like best with high-waisted pants is a cropped, drapey top with some volume. A crop top that is slightly longer in the back does work well. You can wear high-waisted pants with a tucked-in top, too, but I think it's trickier (but not impossible) to look chic that way.
Having said all that, I don't wear them myself. The high rise is supposed to make your legs look long, but on my petite frame, it makes my waist look incredibly short, which is so unflattering that it's not worth the leg-lengthening effect. It doesn't help that my husband thinks they're hideous on everybody (I think he's wrong, they do look good on some people, but not on me!). I think they work better on average-sized and tall women, and women with a more pronounced waist.