We visited in the winter (late June) and were thrilled with the accommodations and location. You can walk to the beach easily and the area itself is well-lit with many eateries & shops.
The flat is in an apartment building on the top floor - the elevator only operates with a special FOB; we felt quite safe. We didn't use the rooftop except to take photos of the amazing sunrise. Jarmo offered an additional cot and bed as well as stroller as we had a baby with us; Terrje offered to move/remove items to provide more room once we arrived and also helped with our luggage! Everything was JUST as advertised, and absolutely clean. The bed was very comfortable, with plenty of pillows. There were extra blankets, lots of towels, umbrellas; even milk in the fridge on our arrival. The kitchen area was more than adequate. Providing a mobile was above and beyond! While we didn't use it, having it available was very thoughtful. We didn't use the television much, but it is a smart TV with Netflix, etc. The wi-fi was excellent.
Staying in Manly was a very affordable way to enjoy Sydney. The Fast Ferry (Manly Wharf is just a few blocks away) took us to Sydney Harbour in about 22 minutes for less than AU$8 a trip. It departs from a different pier at the wharf from the regular ferry which is a tad cheaper but takes over 30 min. In comparison, Taxi/Uber was about $50 to the Harbour. We used Uber from the airport which was AU$60; much cheaper than taxi or service.
We truly enjoyed ourselves and felt very welcome; Jarmo checked in with us throughout the week as well. He was eager for us to have a pleasant stay, not just have a business transaction.
Should we visit Sydney again, we will be sure to use one of his properties!