Fanfiction, real work?

I write the occasional fanfic (Star Trek and Quantum Leap - yes, I am a geek). I think that any writing helps with the overall understanding and furtherance of the process. I think you learn about plot development, for one thing. But I also think you can stunt yourself if you depend too much on characters created by someone else, or a world created by someone else.

As for prizes, the best prize is being able to write for the show(s) you're emulating, which I believe Trek did at least once (I think it was with Deep Space Nine but I could be really off-base there).

i write fanfiction...
harry potter... naruto....
i find it so much easier to write than with my own characters and people who read them already have a feel of the people being read about
i'm not sure if it should be prized as original work.. because the chances are someone's already thoughtt of the exact same thing and the characters aren't your own
i do agree with jespah that just simply writting about something improves your writting ability overall

but the question i constently find askiking myself is where's the sense of accomplishment
i wrtie on fanfiction.net... so i get reviews
and i guess i kinda see my work in print
but it's nto really my own is it??