Highly recommended. Marcus was a great and responsive host and we had a fantastic time staying at his apartment. The location was really spectacular -- dozens of restaurants and bars in Oslo's central city within a 10 minute walk. It served as a perfect base for our group to explore Oslo for the first time. The apartment is modern and comfortable, and very clean when we arrived.
Only possible downside is that it's a relatively small apartment (which I would say you should expect at this price point in the middle of a big and expensive city). But if you bring a lot of people and a lot of stuff, it might be a tad tight. But really, if you're renting this apartment, you should be out and about experiencing Oslo, not sitting in an apartment.