I stayed at Comfort Hotel at Kungsbron 1 in Stockholm, Sweden a while ago, and while this is probably not the cheapest form of accomodation you can find in this rather expensive city, it is cheap compared to the other hotels in this city, but it does by no means look cheap!
The only thing one could complain about might be that the rooms are a bit small, but they are clean, they have a bathroom and shower and everything else you need, the breakfast is amazing and the service is great as well.
So if you want a nice, modern and clean room, but aren't planning on staying in it all day, I can highly recommend Comfort Hotel. It's great for travellers on a budget!