I have had mostly positive experiences with psychotherapists & psychologists.
My wife & I did initially go to the therapist we have been seeing off & on for a few years two days after I first admitted to her that I "might need to see someone about my desire to be female". When I suggested that I go seek out a therapist with experience treating patients for gender issues, he said that that was a good idea & to keep him posted.
We saw him again two days later. My wife had just spent 40 hours in the grips of a huge anxiety attack, completely unable to deal with what I had told her. She had eaten nothing but two small yogurts & had only left her bed once - to go to the bathroom. As I sat there, he reached in to her with exactly the right words to gently pull her out of her anxiety attack and return to being able to face the world again. When we left to go home at the end of the session, she was back to her old self. My wife has been seeing him each week since, and I join her on days when I am not seeing my gender therapist. I found my therapist through Dr McGinn's website & have been seeing her once most weeks for over a year now. I find that by now we spend most of our time addressing issues other than gender. My hoarding is a much bigger threat to my marriage than my gender identity. I also seem to have quite a few autism-spectrum behaviours that are becoming more problematic. The cover-ups that used to hide them have not been working very well over the past few years.
When at a routine visit to my urologist last year, she noticed that my depression was particularly bad and was strongly recommended to see a psychiatrist who could prescribe medication. (One of the reasons I trust my urologist is the fact that she does not mince her words - she is very direct.) She said quite bluntly that many who suffer from untreated depression as badly as I was at that time tend to commit suicide. She followed up on that by making sure I did actually make & keep an appointment with a psychiatrist.
As it happens, the psychiatrist I chose was very much accustomed to patients who saw him as nothing more than a dispensary for whatever meds they wanted. He did not seem to realise that I was unlike his usual patients in that I did not want any medication unless absolutely necessary. He was half-way through writing a script for an anti-depressant I had been on before (that I had stopped because it wasn't helping) by the time I managed to pull my pre-printed list of current medication out of my pocket & give it to him. The entire consultation lasted a bit less than 10 minutes. This seemed short for an initial consultation. The anti-depressant gave me a bad case of serotonin syndrome & I had to stop after a week. I failed to appear for my follow up appointment. Mostly due to a lack of trust.
My wife was sent to a psychiatrist who specializes in treating cancer survivors with PTSD-like symptoms after she went through several tests & specialists panicking about having cancer again last month (it turned out to be an infection). I went with her. The psychiatrist asked many excellent questions and alleviated much of my wife's distress even in that one session. Upon hearing something of my story (trans, ADD, autism-spectrum, addict, etc.), she recommended I see one of her colleagues who specializes in childhood ailments. I made the appointment for this morning & met with her. It was a very encouraging start and I am hopeful that some of the issues that continue to hold me back will finally be addressed. I felt good when she told me that I was giving her a lot of hope about what her younger patients could overcome with how well I seemed to be getting through all the childhood issues I had survived (the list above is incomplete). She said it in a way that complimented how I am dealing with the issues while also acknowledging that the issues are real and do exist. This is in stark contrast to how the adults in my life responed to me when I was a child/teen. They always assumed that if I could make something look good, that that meant the problem was gone forever.
Note that none of these mental health practitioners had any experience dealing with a trans person (except the gender therapist). I received some questions that revealed that lack of experience, but I did not meet with any intolerance or unwillingness to address whatever issue was presenting itself. My experience so far with non-trans-aware health practitioners in general has been positive in that regard. None have refused to treat me (although it take me a little time to train my GP

), and all have shown a willingness to learn whatever they need to know in order to continue treating me as their patient. Maybe it's something about me, but it's more likely something to do with the fact that I live in Philadelphia.
That was a much longer ramble than I thought it was going to be. I hope someone finds something useful there

Be well,
Tessa