I just played through the OSX version, this was the best time I've had playing IWD. Nella, Severn, and Teri were particularly great, though Holvir only suffered as my protagonist was a paladin so there was a certain, "Yeah, I know. Yep, got it" aspect with Holvir's explanations of duty, honor, etc. I think Korin just wasn't my cup of tea, but I spec'd him as an Archer so he was invaluable. Nella in particular really grew on me; I initially thought, "Oh, great, another sad druid" but she was so elegantly written I was really taken with her, and her romance was easily as satisfying as the BG II ones.
I had always thought IWD suffered next to BG; with IWD NPC it was really wonderful.