I love these. The colour is uniform and opaque in a way that Sharpies or Microns just aren't (I love those brands too, but they are not opaque like these ones.
The pens with the edge are slightly oval, which gives them a very comfortable weight, and increases control.
And the choices of colours are mouth watering.
I haven't had them long enough to speak to longevity.
One warning: they bleed through thin paper.