I don't know if I was too young at the time to have any actual proper thoughts on the issue (being only 19 now), but to me anyway, the first time I watched it through completely about 5 years ago, I thought the main point wasn't so much that she was just a replacement for Kes or to look good. But to me it was more like a combination of the fact she is female and borg. It was the first time we'd seen a female borg character. If this character was male, I think it might have been harder to make the relationship she had with Janeway as believable.
I'm not so sure about this point, but I think people don't want to see a male character who is weak and vulnerable. I don't believe she was just eyecandy, her character also helped to develop many others, like Kim, Janeway and the Doctor. It explored the fact that it doesn't matter where you come from, you can still be accepted by others.
This post might not read through too well, but after all, it's friday night