There are two extremes in how people work. On one end you have the people who want very specific tasks which fit well within their skill set. No surprises, do the job, and you're done. On the other extreme, you have people who believe they can do ANYTHING and are constantly outside their existing skill set trying to learn new things.
I don't want to work with people in either of these extremes. Doing the assigned task is dull work and you while you don't get any bad surprises, you don't get any pleasant ones, either. You have to push your limits to learn and grow and make discoveries.
But, I hate working with the guy who thinks he can do anything because he constantly fails. You're always getting bad surprises with this person, and rarely pleasant surprises. Getting the job done sometimes requires finding someone who can actually do it. And one of the things this person never seems to learn is that there are some things you just aren't going to be good at.
Delivering creative services is a balance between being creative and actually delivering a product at the end of the day. I think the over confident, over creative type forgets about the day-to-day work involved in delivering, and the plodder forgets about pushing the boundaries and being creative.