Since it's a little late at night I'm not going to take the time to read other people's comments, with that said here is my tidbit:
You do not need any experience in traditional art in order to make digital art.
Because all you need is the power of observation, time and practice.
And that's it.
I say this because I actually did very poorly in my traditional art classes, even after improving I still sucked at it. Since I had no money to keep practicing after I had finished my classes I turned to the computer and found some free programs to use, one of them being GIMP. I got a tablet for a Christmas gift two years ago and I haven't put it down since and look at the progress I've made with simple observation, time and practice:
Beginning without a tablet: [link] Middle with one year of practicing on a tablet: [link] Current with two years of practicing with a tablet: [link]
This is not to say that a tablet has made all the difference. A mouse could produce such improvements as well with enough time and effort. Although I started out with traditional art classes I could have made the exact same progress being exclusively digital. And no, you don't need to have experience with digital art to make traditional art- they are their own separate mediums and people will specialize in what they can afford/are comfortable with.
If you have talent with traditional art you will be able to have it in digital. The only difference other than mediums is the tools it take to do so. I have yet to find anyone way better at digital than they were at traditional drawings and sketches, and the more you practice, the more you put time and effort into your work, the more obvious it is to those who view it. I would say that digital is a way to upgrade your traditional work into a more aesthetically pleasing view for most crowds of people. Though, traditional just has its own vibe. Regardless, the skill transfer only goes one way in my opinion. Traditional -> Digital. To do it the other way would be interesting, but unlikely as effective.
If you are one of those people who draw fantastically on the computer, without having any actual skill with a pencil and paper, then you are probably one of those jerks who cheats by splicing, manipulating and using various other tricks that photoshop gives you. I am sorry if i offend anyone but i get really angry when i spend like 10+ hours on my projects and get a "good job" and then some little jackass comes in shows off a 3 hours at the most photomanip or vector work and everyone is like "OMG YOU ARE SO EFFING BRILLIANT!" So yeah, If you ask me, you should be a decent traditional artist before moving onto digital art or you are just going to look like a dick.
I hummed and harred over this one for a bit then finally selected yes. It's by no means a black and white question, and of course all artists will be different in quite fundamental ways... but! Yes we knew there had to be a but coming... drawing is drawing is drawing and it doesn't matter what tools you use to draw, your skill with a pencil/pen/brush/airbrush/stylus/palette knife/(mouse)/etc... will always inform your skill with any other medium and a pencil will always be a good place to start your artistic development. It teaches you about different pressures, angles of attack, density of mark and many other things that are specifically relevant to all art that you will produce throughout your life. It's kind of a 'learn to walk before you run' situation.
So I guess I'm not saying that you can't create high quality digital art without learning to draw on paper first, but I am saying that anyone who does learn to draw before learning to use a computer is going to have a significant leg-up against others because the basic skills that they need to use [any] tool are already forming that solid foundation that the artist will then extrapolate from in their experimentation. Final message: don't really on the automated functions of your software too much, ctrl+z is a useful tool but it can become a crutch without care and consideration; I remember in one of my first formal art classes the teacher told us all to get out our erasers, he walked around the classroom and picked them each up without saying anything. Once he'd made his way around everyone he threw them all in the bin and announced "these are useless. All the marks you make are important, they make up the body and life of your art. A true artist doesn't work against what they produce, they work with it. Creation is an organic process, what you thought of as a mistake might in fact be the thing that makes your work unique and special. Work with your surface, and work with your tools - never erase your work because it is all important." Now, I must admit that I pick and choose when to follow this advice, but I think it's fundamentally important.