For me, this is my first MMO, and to be honest I am enjoying it a lot, this may be because I absolutely LOVE Star Wars, or that it is my first MMO and I'm not sure what other games have better and what is bad. I played my character as a smart, cunning, courages and kind Jedi Guardian, and every choice I have made has been Light side. My character in my Legacy is the Son of a member of the Dark Council so he also has an ability to use certain Dark traits and powers that can help him on his ways. He draws upon the light and dark, but does not believe in the practices of the Sith.
On Tython, I had lots of fun and found lvling and learning a fun experience. It also helped me mold my character into what I and the game would perceive of him. From Coruscant till the end of Ord Mantel, I wanted to slit my risks and put pins into my eyes. The story wasn't all to bad, but everything else was so boring and bland. From there on I think i have ****** on several occasions while playing this game just because of the sheer awesomeness.
In my opinion, it really comes to what you like and how you can perceive your character. In my mind when i play the game I am constantly thinking of my choices and how my character would play out certain situations. I strongly recommend you to play the JK class, it is almost impossible to get a true grasp of how the story plays out and what you would take from it by reading forums. If I was in your shoes, play to lvl 30-35 and see what you think, after that i would not bother (but when you go to the emperors fortress with the other Jedi and fight scourge, from there on turns into total complete epicness, well for me