We just returned from a wonderful few days at Vedran's place. First, you should know that the apartment is even more lovely and well-appointed than the photos. Stylish with lots of space (especially in the bathroom, which was positively expansive by European standards!) and located right in the heart of everything, this is a great place to stay for someone visiting Oslo from out of town.
We visited to attend the opera and we picked the perfect place to stay for that. The opera is a quick and easy walk up the road (even for an out of shape American like me). Along the way, there are tons of shops, restaurants, and neat art installations to see. The Munch Museum was also a fun place to visit and a quick walk. Finally, the Central train station is also right across from the opera house, so we were able to take the train right to and from the airport for about $10 US. Super easy, fast, and convenient.
Vedran was very helpful with great suggestions and communication. Would stay again!