don't get me wrong; i love my half-sister like a... well, like a sister. but i never see her mentioned in any of the "worst npc" lists. here's my nomination.
1. she arrives VERY late. unless you have a "core" party of only 2-3 npc's and pick up extras just for their quests, you've probably got all of your bases covered once you get her.
2. the first time you played you no doubt wasted all those scrolls in irenicus' dungeon by letting her read them, not realizing she was about to leave for the next 3 chapters. then, when you get her back, you've got to be carrying one or two scroll cases of spells if you're planning on her being your primary mage.
3. her theif skills are irrelevant. yoshi is dead and there is no other single-class thief npc, so unless you're replacing yoshi's thieving or subbing nalia out, more than likely you've already got a thief far better.
4. MY BIGGEST COMPLAINT: she has LAME DIALOGUES! considering her importance and relevance to both your character and the plot, she has ZERO interactions with any of the other npc's, and most of what she says to you is rather generic. i've read all the rants about how boring valygar is; well, imoen is at least as bad. even if her class(es) were something i could use, i wouldn't keep her. she is, at best, boring, and at worst, depressing and redundant.
i think the bias in favor of imoen stems largely from the irrational emotional fact of her being "related", though i strongly doubt there's any legitimate genetic kinship but rather a similar "essence" or "spirit". in one of the early dreams where she asks you if you remember saravok, she says something like "he sought your death, and mine". uh, excuse me? there was NOTHING in bg1 to indicate that saravok cared one whit about imoen; nor did elminster, or the harpers, etc etc. this is called revisionism and is almost repulsive.
there's my 2 cents. disagree with me if you dare
