I have pretty dark brown hair, I had highlights put in this year and I really like them. I am very pale and didn't want reddy colours in my hair so my hairdresser has very finely put light brown/honey colours through. It looks pretty natural but has brightened up my hair nicely andcoveredthegreys.
I was worried about upkeep and roots, but I managed to go five months in between dyeing and it looked fine!
I have reddish brown hair and have some highlights. They're platinum blonde and in random places but mainly under the top layer of hair. Means it looks pretty 3D when it's down (just on shoulders) and even more interesting when up.
I don't have lots of greys, but kept finding stray bright white hairs which really stood out against my dark hair so my highlights have covered it nicely. I used to feel very self concious about them whereas now I don't. As I said my upkeep has been easy, once every five months.