I like the refillable aspect (though I'm told you can revive Prismacolor markers with Isorppyl Alcohol. I've yet to try), the brush tips, and the color palette they are available with. I also think they smell less than Prismacolor markers and Sharpies.
The airbrush add-on is pretty interesting, but I can't figure out how to airbrush correctly and buying air cans kind of builds up and air compressors are a bit hefty on the price too.
But Copics are a bit expensive. Well, they're less expensive with some hunting around the internet... or at least there's snagging free shipping?
...and currently I've moved on to an obsession with ink and watercolor... so my set of Copics, half of which are dry, have been sitting in my drawer for like a year... I don't want to toss them because I can refill them, but I haven't felt like using them. sweatdrop
I used to buy them back in high school before I knew what money meant. I still have some of the things I colored with them, and I gotta say, they can make even a crappy drawing look really appealing.
On the flip side, my time as an undergrad drawing major was all about finding the cheapest ways to make art. Like: "how can I make this piece with a couple of scraps of colored paper and an xacto blade?" Knowing how to MacGyver your art can be just as valuable as knowing how to use the nice tools.
Long and short is that copics are amazing but they're a bit of a luxury.
I use the Copic Sketch Markers and ink liners.(you will need good bristol board or marker paper too) Built a custom set of 72 for about $320 through ebay/DickBlick. They are radically different from Prismacolor. The colors paint on very well, and have a lot of transperancy to them adding to the typical "manga" look of a drawing. If you are going to be doing a lot of marker work I'd go with Copics. If you just wanna do a few drawings, go with the Nikko or Prisma. Otherwise, get yourself a nice Wacom tablet. I do the majority of my screentones and coloring in Photoshop even after getting my marker set.
Everyone is so right. Copic is RIDICULOUSLY expensive. I've never even been lucky enough to own just one marker. I have the pens, but I'd love some markers.
I will say, however, that in my opinion they are worth the money in some respect. They're a great tool, like someone say "luxurious", but that's what they're charging you for. Jerks. I just want some markers...