What a cracking spot! We spent 8 nights here, the first 4 during the Tons of Rock festival (only 15mins walk away) and then 4 whilst we took in Oslo.
The apartment is exactly as described, and the view is magnificent - especially at Midsummer! Simply but fully furnished - which is what you need, why would you want to stay in when in Oslo? Hot water is immediate and the shower very therapeutic - perfect for when you're still clarted up with sun protection given the amazing weather we had this past week!
Main thing - if you're walking be prepared for a 350step near-vertical hill as you pass the pizza place... So ideally get the bus (34/72) and take the very graceful, slightly downhill 2minute bounce instead of lugging cases and backpacks in an 80s training montage way...
I will return here if I'm in Oslo again... highly recommended...