It.. depends. We were Baker-Acted twice (USA). Lemme format a simple "pros and cons" list.
Keep in mind we were a minor at the time, so it may be different, but I have combined my experiences with ones from others to create this list. Still, use caution.
Pros:
• If you are non-judgmental person in the case of mental illness (you are on this website, so I assume you are at least a little bit), you may find some people you connect with. I found comfort in two people in particular, both diagnosed with schizophrenia. One more "mild," one more "severe."
A trans man named Evan, I believe, had a form of schizophrenia that caused his drawings to talk to him, full personality and all. He showed me his sketchbook, was very self aware. He was my first experience with trans people, back when I thought I myself was cis. He made a lasting impression on me, and I wish I had contact with him.
The second person was a girl with "full-blown" schizophrenia. Seeing people, voices, even delusions she was black (she was not). Everyone avoided her and.. I knew that feeling. So, we struck up conversation. She was very kind.
For adults, this will likely be much different, but I have heard stories of people who have found community as an adult. The tips I've gotten essentially say, when finding friends, don't focus too much on what disorders you share, that can lead to problems. Focus on your likes, hobbies. I connected with Evan over our shared love of art, for example.
Another note: In a mental hospital, you will find people who aren't very nice, sometimes even quite nasty. Try to avoid the "numb" ones who won't change no matter what. In my experience, if one is aggressively complaining about the food, I would pipe up something like "Ugh, I know the feeling." Their reaction to that shows a lot about a person.
A roll of the eyes: Avoid
Ignoring you: Likely avoid
Agree, nod to you, anything of the sort: Proceed with caution
Use your response to prove a point or escalate the situation: Definitely avoid
Get aggressive towards you in any way: RUN. This is why this may not be a good idea to try for just anyone.
If you don't have skills to read people, an institution may be harder to navigate for you.
• Typically has a set routine. If you are tired of the monotony of life, this is a con. If you have autism, anxiety, OCD, or just a love of routine, it's definitely a pro.
• If you do not want to harm yourself, it would be extremely hard to do so while there.
• Benefits for good behavior. This depends on where you go. The one I went to had an outdoor section, with a pool.
• Activities. This also depends on where you go. The place I was in focused very heavily on art. They also had reading, sometimes movies.
Cons:
• "Cavity searches." They have you take off your clothes and cough while squatting. Unsure what happens if you refuse.
• "Booty juice." That is what the people there called the anesthetic (administered in the buttock) for aggression. I assume this is different for adults but I'm not sure enough to leave it off this list.
• Ironically, not very disability accessible. Took away my Fidget Cube I used for my autism/ADHD, claiming it could be used as a weapon (yet gave us sharpened pencils).
Floors are slippery. They took our blood the first day there, and didn't have access to a butterfly needle or numbing cream (both things I used due to a chronic fear of needles).
Very bright lights, strong scent of cleaner, often loud, overstimulating. They also didn't have very many food options for people with ARFID.
They give you a short amount to shower, which can be hard for people with low dexterity, and also wait outside with only a curtain, no door, which can be hard for sexual assault survivors.
They have only plastic sheets, which can be horrible for people with skin conditions or chronic pain. They had us share rooms, so it may be hard to sleep for people with hypersensitive hearing. Not to mention PTSD, and I can't imagine the dysphoria of being roomed with girls if I knew I was trans then.
• No shoelaces. No strings or straps on clothes. No piercings. I was not informed properly ahead of time and all of my clothes were confiscated. I wore scrubs.
• Can be boring. Very boring.
• Who will pay for it? Better have good insurance.
• I can't think of more, but there are certainly more cons than pros.
Hope this helps.