These were a really hot item this year in the crafting world and I would say that as a general statement, I like them for use with watercolor techniques more than straight lettering. They differ from other pens because they have a real bristle brush so you can achieve a really great variation of thin to thick. However, they almost will always give that brushed look to the strokes so it's not ideal for larger pieces of lettering.
Watercolor lettering with them is great and they have beautiful color options. I've linked to the 24 set above but they have larger sets available too. I have the 24 and I think its sufficient because you can always blend colors together to make more! Whether you use a slick surface like the acrylic block in my video to pick up the pigment or you don't even use water and you blend the colors together with just the tips of the markers themselves, these are versatile for crafting and experimenting with color techniques in your work or hobby.