We had a wonderfull time in Oslo.
We stayed at Jarle´s apartment for four days. It was just the perfect thing for us - our kids simply loved all the toys, and the playground downstairs also. For the rest, all very nice and confortable.
We had some meals at home, and found a completely functional kitchen, with everything we could ever need.
The neighborhood is a lively place with lot's of people and animation, but the apartment is very calm and there wasn't any noise or other disconfort.
Public transport services to everywhere are also very good, with good frequences - It's a 5 minute trip to city center.
If you're travelling with small kids as we were (5 and 2 year old), Jarle's apartment is really a good option.