Oh, I hate her as well, though not for the reason you listed. I think all followers do that. Even Brynjolf likes to fight rather than sneak around.
forced quest followers always seem to give me away when I'm trying to sneak. Her as a follower later is alright. She's a decent follower (using a mod that turns her into one after the skeleton key gets returned)
well 99% maybe.
I for one like her even if I find the story weak and dislike being shackled to Nocturnal. My only dislike for Karliah is her voice. Now before you misunderstand me, I'll be clear. Its not so much her voice but the audible level at which she speaks. STOP WHISPERING!
Otherwise I wish there was more dunmer followers like her to have around.
I was almost through sneaking through the slave pits when Brynjolf decided that he had to break sneak and attack the Falmer because honor demanded it. It was very annoying.
Yes, that was the only thing I disliked about Karliah too. I was forced to adjust my computer audio volume and all of the audio sliders in the game to compensate for the low volume Bethesda at which recorded her audio files.