I'm glad to hear you are still enjoying it, but is non-linearity really a requisite for an RPG? I mean, in know choice and consequence is the new thing, but I don't remember most early RPG's giving you much freedom with the main storyline.
Most of the role-playing tends to take place as I explore the huge living world. I found a house recently where a drunken father was berating his son. Now I could have just walked away, in fact that was my intention, but they noticed me and the dad turned his anger my way. At first I went to leave, but he pulled a gun, and I ended up putting him down. The son ran to his bed to cower in his room. I figured I'd might as well loot the place, and I found a letter from the kid's mom that the dad had been keeping from him. After I stole all their money and stuff, I let the kid know about the mom. See, I'm role-playing a good guy!
Also replayability for me will be the fact I will want to keep playing and exploring after the main story is over.