Personally.. I think a good artist consists of a creative mind and a talented hand.
Copying well means that you have a talented hand... and then progressing to original work adds the creativity.
I've always said I'd rather be creative than talented. I respect people that have the talent, but lack the creativity or style. But rarely do they capture the same amount of respect that I have for creative individuals. I'd rather see a person who is lacks the talent, but makes up for it in style.
That being said, copying IS a pivotal part of growing as an artist. Now, if you've been drawing for years upon years, and you still rely on copying other artists, you haven't grown.
What about this? It's one thing to copy comic art, but how do you feel about people that do portraitures? Technically, they are copying. Right? Not in my opinion. I mean, I have a friend that does portraitures. I give him a hard time about it, saying "just take a photo, it's easier." But in the end, I really respect two things about it. 1) He IS very talented, a talent I do not possess. I CANNOT do potraits. I cannot draw people that actually look like the person. 2) He still manages to make every picture look like his style. If I ever saw a new pic by him online somewhere, I would know instantly it's him.
I guess the main difference there is, if someone copies a comic artist, you will always be able to tell who that person copied. You will always be able to look at my art and know I've copied Jhonen Vasquez and Mike Mignola enough times it is now embedded in everything I draw. But, if you "copy" photos, often it still achieves a feeling of "hey, that's Harrison Ford in a style I haven't seen before."
I don't really know where I'm going with all that. I just felt like throwing in that little bit of thought process to this discussion.