When approaching an art elephant, you should do so with caution, if by chance it does not relate well to you, you could be cast aside like a bad peanut. How do you relate to an art elephant, you ask? Actually, they don't mind if you are clueless and want to dabble in order to discover your talents, but if you got skills and attempt to force the issue, they can be quite rude.
My law of thumbs is like this, if you have a traditional painting or drawing background, then digital raster type painting and drawing will be a pleasant encounter. Folks who do desktop publishing, line illustration, perhaps Cad (like me!) will find friends with vector drawing. I think a mix of talents is good, game artist and cartoonist do 2D, 3D modeling, surface textures and background painting. And as we all know there are a glut of photo buffs. It is OK not to be able to do everything, learn what you need to know.
Approach straight on, an open mind, be fearless. Don't come in from the side like you know this beast, many are surprised by how agile the art elephant is to turn and trample, "I didn't know they could now do that!!". Yes, there are big game hunters (graphics pros) who don't always have good things to say about Open Source Graphics Apps. I think they are too fond of their zoo animals behind bars. I have met several who hide their wounds behind flack jackets or wear their pit helmets indoors. The Open Source Jungle is safer for learners than for ones who presume to know. They say "that elephant" is still under development, it doesn't do this, and it can't do that. Then they walk away assuming the elephant won't change, won't improve, won't evolve and can't possibly compete with the caged animal they are use to.
Unbeknown to the mainstream, though whispers might be heard, in a clearing in the Open Source Jungle, a billboard touting the virtues of art elephants in the wild with bold letters, "WE CAN DO IT ALL! (though mileage may vary)". Just because there are no big established company names behind Open Source Graphics, don't think it is a static, hopeless and futile situation.
Mostly it is about spending enough time with an application to where you learn what it can do and what you can do with it. What artist does not devise his own tools? I find it is production artist who insist a tool be there and criticize if it is not. This is a good thing as the pros often initiate the further development of good software. The very cool stuff we use today was very wimpy yesterday and will be the killer app tomorrow. You can almost apply Darwin's theory to software, if it sustains long enough, it will evolve, even persist, maybe even dominate.
Most artist aspire to have the most developed, advanced and "in use" graphics software they can get, even if they are beginners, even if they only use it occasionally. They want the industry standard at all cost and will pirate if necessary. I want to emphasize that it is the tools themselves and the file formats that matter. If you can get the tools and produce the file formats for less money, you are ahead of the game. If you are locked into the professional track with must have software, I can't help you. If you have options, choices and wiggle room, by all means give Open Source Graphics Applications a shot. You don't need the whole bakery shop in order to have a loaf of bread.
I know art elephants are a temperamental lot and I don't want you to use Linux just because I say so. I think it's a better choice, but we can compromise with Open Source Apps which run on Linux or Windows. And I say this because some graphics hardware, pen tablets in particular, may or may not work under Linux. Wacom tablets are supported under the Linux Wacom project. Wacoms are normally Windows compatible as are any other graphics tablets. So, Windows platform PCs can use any tablet that does the job, where as Linux platform PCs should stick with Wacom tablets. The good thing is that many tablet users upgrade and resell their older tablets. If it does the job at a small price, you win again.
Now that you have become symbiont to several art elephants in the herd, you will want to connect with others in the same situation. The Linux Graphics Users is a good place to start, the forum is wonderful. Also the Wacom Community page is cool. If you need some encouragement in digital art, http://www.karencarr.com/how-you-can-paint-using-digital-tools-and-software.php
Now as your Linux guide and art elephant herder, I say, "Get out there and dabble!!!"