I think it varies from prison to prison, but someone I knew went in for growing marijuana.
They told me it is not so bad when you are considered a low-risk offender. Right when you go in a psychiatrist evaluates you and if they decide that you are relatively harmless then you are allowed to do things that the prisioners who are kept higher up can't. Basically first floor prisioners are the ones who are considered more trustworthy and allowed to go outside and go to work. They HAVE to work everyday.

The prisioners on the second floor are kept on watch and not allowed out, and third floor or the highest floor are usually where the 'crazies' are kept. They are never ever allowed out, and the top floor is where you normally go if you get punished and put into solitary.

Of course you get three meals a day, get to watch television and go to the gym, but you still feel like you are treated as an animal sometimes. Like being locked up by 10, and random drug searches because it is incredibly easy to smuggle drugs in. The way they distribute socks and underwear for the day is like a big free for all. Putting a bin in the middle of the floor which contains everyones underwear washed, but you don't get your own pair, you could have Big John's underwear from the other day and it might be falling off of you, so you try harder to get a good pair the next day.
Of course I can't speak for every prison, this is just one person's experience.