The one piece units normally found in condos, townhouses etc? I looked at a couple. They are nice because they usually are older mechanical with not a lot of electronics to break. I say a pretty good one by Whirlpool with a 3.2 cu ft washer. They usually have smaller washers.
It is about $900 to 1000 versus a stack with fancy front loaders about the same price.
If you are referring to the combo washer/dryer unit then you will be happy if you only need to wash a half-load at a time and don't mind waiting four hours for it to finish with clothes so wrinkled it takes twice as long to iron them.