I used to really like Tara because I could relate to her being so shy, but now looking back, IMO they really didn't do a lot with her. I think the relationship with Willow held her back quite a bit if anything, and it seemed they only really began developing her in season 6. And of course that was most likely just so viewers would mourn her death more.

I would have liked to have seen more of a friendship with Buffy developing, it was there so briefly. More Tara/Dawn scenes would also have been good. They were adorable in Smashed