My girlfriend and I stayed at Copenhagen Downtown Hostel for two nights in a private ensuite room. It's what you would expect from a hostel. The room was clean and comfy, though you shouldn't expect to use it for anything more than sleeping, washing, and leaving your luggage as it is small. The staff were helpful and check in/out was easy.
There is a lively bar on the ground floor and a few bars in the street that are open till late. If you want a quieter night you can ask the staff for a quieter room and they will put you on one of the higher floors. We were on the forth floor and you could hear people on the street for most of the night but not loud enough to keep us awake. I wouldn't recommend here if you want a completely quiet night as there will be some noise.
We didn't have the breakfast though from what I could see you get some cereals, toast and some cold meats, no cooked food. For the price I wouldn't recommend it. What I would recommend is going to the bakery called Emmerys down the street, the pastries and coffee was great and reasonably priced.
We would definitely stay here again.