Because I live in MA and voluntarily hospitalized myself, I managed to score McLean, one of the top hospitals in the country. A very popular hospital with a world-class staff you may or may not see. Also the same hospital in Girl, Interrupted.
My stay was very dull for the most part, but I enjoyed the attention I was getting. I purposefully packed clothing that was somewhat excessively formal, which was noted on my chart in a positive way as "dressed neatly". My affect was listed as "blunted" and my affect and mood were listed as "depressed". I was told I spoke slowly, showed little emotion even when describing my suicidal thoughts and behavior, but was readily friendly, proper, and affable.
The place could be amusing at times. My treatment team there thought I would make for a perfect subject to be interviewed by the famed Dr. Maltsberger about my suicidality, who has a hell of a reputation; one of his essays is even published in a book of mine. Aside from the stupid number of medical students there which I should have asked to leave, it was a pleasant interview in which I had a lot of fun. He asked me all about my previous suicide attempts, my current plan, and he asked me a lot about my past, particularly with my parents. I took a rather perverse pleasure in admitting to him with a friendly smile my violent suicide plans and looked him in the eye as I said it, curious as to how he'd react.
I did poorly on his cognitive tests, though. I generally do well on those kinds of tests, but some of them trip me up, especially anything related to memory. They were simple enough, but I continued to make mistakes. For instance, I had to subtract 7 from 100 and then another 7 from that until he told me to stop. I made one wrong calculation early on, which was unfortunate because you get a maximum of five points if you do it five times in a row correctly. I believe I messed up right after 93, and one point is pathetic. I also bombed the short-term memory examination, in which he told me a short story, then asked me to tell it back to him, but I really just couldn't because I don't retain auditory information. I was able to mention a few details about the story, but nothing else. But who cares, I was interviewed by the famed Dr. Maltsberger. I wish I had brought my book along with me so he could have signed it.
There was one instance when I became furious at a staff member for patronizing and demeaning me. I responded by self-harming along my arm, after which I immediately asked to speak to the person who was responsible for me that day, telling him what had happened. Needless to say my treatment team asked me about it later, but everyone agreed there was no reason to put me in the ICU, so long as I didn't do it again.
My second roommate, who was a longtime resident patient of the place and who I spent the most time rooming with, was a highly mentally ill and very low-functioning person, which made time with him rather difficult. Although he didn't do anything that was actively destructive, his personality was very disturbed, and very difficult to communicate with. He was also somewhat demanding that I entertain him, usually when I wanted to sit in the room and just read. He asked that I read certain passages of the book I was holding, for instance. It didn't help that I was reading Pride and Prejudice, which is awkward to read aloud. He would persistently demand to be released to the staff. I felt bad for him, really, for being so clearly the type of person who they could not release, even though he clearly was stir-crazy and bored out of his mind, and who had already spent extensive time there and in other units. I very much preferred my first roommate, who made no demands of me and gave me no trouble at all.
The last thing I'd like to mention is that you might run into someone who is malignantly disturbed. For instance, there was one woman in my unit that liked to walk up and down the halls screaming obscenities and threatening the staff in the middle of the night when everyone was trying to sleep. Some people I was with were clearly highly disturbed, and I felt somewhat frightened on occasion, although not so bad that I actively avoided them. There was one man who I accidentally infuriated, apparently because something I did reminded him of his abusive sisters, and we had a small physical scuffle, but nothing serious.
Anyway, that was my experience, although I'm leaving out some details. That was what happened with me, more or less.