Fantastic location for Oslo. You're right in the heart of Grünerløkka with plenty to do nearby. Loads of cafes, bars and restaurants plus very easy access to the city centre either via public transport on foot. The apartment is nice, well lit and comfortable with all the general amenities you'd need for a short stay.
Worth noting, as other reviews have, that the double bed is in fact two separate beds. This wasn't an issue for us though. Apartment could have been a bit cleaner but otherwise was nice. We brought our baby with us and didn't realise the apartment was on the 4th floor with no elevator. That was our fault but do be warned! The host was really accommodating and helped us out with storing our pushchair in the luggage room and arranging a travel cot and high chair.
Would definitely stay again!