Personally, I've never found wee Imoen to be annoying, but then, I have a high pain tolerance when it comes to annoying behavior.

Same goes for Anomen. Actually, I can stomach just about every NPC in the game other than Jaheira. One has to draw the line somewhere, and her constant carping and complaining is just not fun. There's no "humor" to her, where I can find humor in all the others.
I definitely liked Imo better in BG1, her line about "I've done had enough of this!" cracked me up when I heard it the first time.
-Sazerac