The only time I liked Sela was when she stepped out of the shadows at the end of "Redemption Pt. 1". That was shocking because I thought it was Tasha Yar and I didn't know what the heck was going on. I hadn't really caught the references to the character in "The Mind's Eye" so her appearance was totally left field.
My reaction as well, totally. I think that was what gave T.N.G the reputation for having season 'cliffhangers' .
It feels strange how underused the character was after that, she just disappeared. Her appearence in the Spock episode was anti-climatic in my opinion.
It would have been interesting to have the character appear on DS9 after T.N.G ended. She could have been the Romulan that refused to removed the weapons on the Bajoran Moon. Or just in any situation, would have been interesting to see.