I stayed three nights at City Lodge, overall it was a good hostel. I'd recommend it to other travellers.
Pros:
-great stuff (majority of them are really willing to help)
-comfy beds
-very central location,easy to move around
-nice comman area
-guest kitchen (no cooker though only a microwave)
-free computers/wifi
Cons:
-yes, all the room are on the bottom floor of the building with no window
-some people find it very hot but it was ok with me
-only two toilet/showers for the whole hostel

I stayed at this hostel one night. I chose it because it right by the train and bus stations. My room was clean and the people working were nice. The showers and bathrooms were also well kept. As others have mentioned, the rooms don't have windows, but this didn't bother me since I was only there for one night. Sheets and towels cost extra.

I stayed in this hostel with a large group in Stockholm for a sports tournament.

Good points about hostel:
Really good location
free internet
comfy beds
good showers
sinks in some rooms

Bad points:
all rooms dont have windows which make the hostel very hot (the weather outside was only about 20 degrees so if it got hotter it would be unbearable.)
very few showers and toilets

I stayed for two nights, one in a twin room, one in a dorm. The hostel is just a short walk away from the old town, bus terminal and train station. Having hostel's address I had just a small trouble to find it. Room rates are quite high, but still a bit below Stockholm's average. Staff was EXTREMELY helpful ! The twin room was very nice, and so were hostel's common areas. The dormitory was I'd say standard, except of no windows. Bunk beds could be higher, and there wasn't really much space between them, but as I said, standard dorm. There was very weak/no mobile network signal, which bothered me quite a bit - thick walls I guess. Breakfast was 60 SEK extra, good, but pretty much what you get anywhere. Hostel was quiet, and good place to rest, day or night, and definitely is one of the above average ones.