[akhtene]

Feanor was a rebel who dared to rise against powers much stronger than he. And he was seeking justice (at least what he believed was just). Of course he was rash and thoughtless from the start, but for many of us the one who dares to rise against powers for a (seemingly) fair cause acquires some romantic image.
Another thing - Feanor's role in the history of Middle-Earth. Whatever his intentions were, but he brought High Elves back to M-E. Without this deed of his we could have never known Galadriel, Gil-Galad, Elrond etc. And what would have become of Men? The elves who had remained in M-E didn't seem to care much for Men (or am I wrong here?) But Noldor befrended some of them and anywhay they resisted Morgoth and Sauron to the last.

So I believe that the role Feanor played for M-E couldn't be underrated. As for his personal qualities and means he used - everyone can judge.