We had a really good time at Ida and Mohammed's house. They made us feel very welcome and also gave us great tipps about what to visit in Kobenhavn.
Their place is very nice, a cute, 'hyggelig' house close to the city center; the bus can be reached within a few minutes; it goes to the center/from the center every few minutes, even during the night.
They were even flexible with our time of arrival and also the communication before our arrival worked out very well. :-)

I can only recommend staying at their place, they are really nice people and great hosts!