I've been in three acute psychiatric wards and two residential treatment centers. I think your experience will very much depend on the program you go to. Some are good and some are downright abusive.
In terms of psych wards, I have personally found my stints in them to be entirely unhelpful. As >>91473
said, treatment is minimal, they are essentially there to keep you from killing yourself. It's like being babysat. I've been lucky in that all three of the psych wards have been decent. Unhelpful, yes, but I wasn't treated poorly by any means. I guess they did keep me from committing suicide so, that's a plus. If you want any specifics on daily life on the ward, feel free to ask.
Residential treatment centers are a different story. You're there for a longer period so treatment is obviously more intense and personalized. I was in my first residential treatment center when I was 16 for about four months. It helped me to a degree, but I would say the program as a whole was not good. The staff was incompetent, sometimes rude, my therapist was not entirely knowledgeable about my diagnosis and therefore did not have the tools and abilities to treat it, and there was a focus on compliance rather than caring, holistic mental health treatment. I've had nightmares about my time there for years after and many of my friends who I met there have similar things to say about the program (So yes, you can make friends, though you should be careful and know that many people are there to focus on their treatment, not to socialize).
I ended up going to a second residential treatment center when I was 18. This center was much more well-known and acclaimed, but unfortunately my previous experience had tainted the idea of residential and made it difficult for me to settle in so I ended up checking myself after a week or so. From that short time, though, I was able to tell that it was a lot better than the previous program I was in.
So, overall, my suggestion would be to do your research if you decide to go this route. Make sure you know what you're getting into and choose a program that's appropriate for your needs.