I was diagnosed as bipolar (with schizotypal tendencies.) I have also spent quite a bit of time experimenting with salvia along with a variety of other pyschedelics.
I have only ever had one unpleasant experience with salvia which I associate with it being the only time I ever smoked an extract of the leaf. I think it was a 10x. The unpleasantness was two fold...
1) It felt like a fully "mechanical" trip/experience (much like 1,4 butynol but amplified)
2) It lacked the intensity of the experiences I had from smoking straight leaves
I am quite a fan of the dissassociative trip of salvia. I find the disconnect/reconnect sensations of the trip to be quite cathartic. Especially when mixed in with other psychedelics while "cocktail tripping." It is most certainly not a "feel groovy" sort of trip for me. I do not think of any of the experiences I have had were "fun" by any stretch of the term but, all but the one have been enjoyable and rewarding.
MDA/MDMA had significantly more negative impact on my emotional well being than any other substance I ever experimented with as they both trigger depressive episodes for weeks following an experience.
As a sidenote... even my one unpleasant salvia trip was a carnival ride compared to the sensation of being on lithium, now THAT is a fucked up drug. YMMV.
As far as a recomendation about experimenting with salvia I'd say go slow and ease into to it. No sense in trying to storm heaven until you know how you are going to react to the sensations of the trip.
As far as psychotic/near-psychotic episodes go, I have only had one during a psychedelic excursion after severely under-estimating the potency of the mushrooms I was eating. Looking back it was a serious turning point in my emotional growth that allowed me to find a lot more comfort in the mood shifts and, eventually a sense of stability within experiencing my own life.
But, that is a whole other story.
