Karl Johans Gate 35 seems to be the poor stepsister of the adjacent Karl Johan Hotel. It shares a lobby, elevator and breakfast area but the residential space is separate and oriented towards less affluent trravelers.
The air become much more stuffy immediately upon stepping into the 35 wing. The modest single room was uncomfortably warm on a 70 degree (Fahrenheit) day, although it eventually cooled down upon opening the windows and turning on the fan.
I found the mattress and pillow uncomfortable, but that could just be me. The other major sticking point, though, was the nonstop thumping from the nightclub below. I asked for a quiet room and assured that the assigned room (365) was far from the music, I could definitely hear the thumping into the wee hours of the morning.
The location is great and the breakfast buffet is large and varied. However, I really had a problem with the noise and stuffiness, so I can't give a higher rating here.