If you follow along with my hashtag #CopicsLettered on Instagram, you'll know that I am a fan of these pens -- however, I've always shared with my followers that I do think that they are a bit more of intermediate/advanced pen to be using because of their flexible "Super Brush Tip." (The other side of this pen is a Chisel Tip.)
Another thing to note is that this is not an inexpensive purchase. At the lowest I've found, they're about $6/pen but they do have an extensive catalog of colors to choose from and the prime use for these pens are for artistic coloring/drawing. These pens blend like a dream because they are alcohol based and not water-based -- therefore, using a good quality cardstock (like Neenah Solar White) is an excellent way to play around with the color familiies to see what kind of effects you can add to your lettering. I created my hashtag so that I could show another medium to use for lettering but I would say these pens weren't necessarily designed with that in mind.
I enjoy using these for 'special' projects where I want to include some blended coloring on the words I'm writing or a shaded/highlighted effect. They also have a fairly large nib size so they prove to be a good option for writing at a larger scale on a smooth poster board.