I was only on olanzapine (Zyprexa) for a short time, but it was highly effective at extinguishing my mania with mixed features. I remember feeling really good and balanced fast, mood-wise. I mostly took it during a psych hospitalization. I did experience weight gain, as many do, and recall having some mild akathisia, but I don't recall any other notable side effects. I have heard of people who don't experience weight gain or akathisia from this medication.