To be honest, I always liked Sela. Don't get me wrong, the character isn't perfect, but I kinda always liked Sela (despite the fact that it's her fault that her mom is dead & the fact that she hates humans because of her mommy issues). Yesterday's Enterprise is my favorite TNG episode and therefore I found the idea of Sela interesting.
In a manner of speaking she apparently encouraged Ron Moore and David Carson to relocate events of "Yesterday's Enterprise" into a parallel universe (instead of just a changed time line). But it's obviously not a popular idea if you check out reactions in the corresponding Enterprise-C
threads ("TNG" and "fan art").
I found the character interesting. When she first shows up on the Enterprise-D
in "Redemption II" she is all cocky and snippy. But then she talks about her mother and suddenly she becomes insecure and nervous (great acting by Denise Crosby, IMHO). And then she claims that all the humanity in her has vanished, but Picard reacts with a sympathetic smile.
I for one would have liked to see more of her and additional interaction with humans. She was quite the opposite of Spock - him trying to get in touch with his human half, she trying to get rid of it. Plenty of story potential we unfortunately never saw realized.