are there any drawbacks if you dont take imoen at spellhold? i have all my own characters and wanted to know the drawbacks of not taking her? thx.

None at all. I was tempted, because of her low level, to leave her, but kept her just in case. However there is no difference to how the game plays. She does learn more spells per level as she rises than she ought to though, so she soon catches up.Probably a bug or possibly a way of leveling her with higher level parties.