Those who plays/played it. What is your opinion of it?
I generally love it. Mainly because it is considerably story-focused and because it is probably the first Star Wars game where I can actually play an imperial/Sith (I always preferred Empire, to be honest).
I have played through all 8 classes and my favourite are Imperial Agent, Sith Warrior and Sith Inquisitor. Yes, as I said I don't like Republic and Jedi. The only one I like on the republic side was smuggler.
I have some complaints though. I kind of dislike some of the planet designs. For example I hate Belsavis, and to some extent Alderaan, since they looks like something from Lord of the Rings. I also think Nar Shaddaa should have more darker tone (I resent developers turning it into "Las Vegas of Star Wars") but now I got used to it. I also hate the whole Revan storyline. It is sort of ridiculous. They should just left the character alone and not ruin the mystery of his departure in KOTOR. Finally, I absolutely hate the whole "almighty" Emperor guy. I think they went far beyond the point of "good taste" with him.
On the other hand, I really like Tatooine design. It visually perfect. Maybe that's where my obsession with clear blue sky and nice desert scenery come from (referring to Gilbert Taylor thread discussion). :)