The location is perfect, walk to gondola, bus, train, cafes in a couple of minutes.
The apartment was very comfortable for our family group of 6 adults. Whilst not spectacular mountain views from inside, nice windows looking out on the street from 2nd floor (Brits would call it 1st floor, ie one up from ground), though the bunk room only has a window to the apartment stairwell, not the outside proper, so less bright and ventilated than the other three bedrooms. Kitchen well equipped - we cooked 7 breakfasts and 2 suppers with ease. The lounge/dining is full of solid furniture so feels cramped, but was fine. Laundry doubles as a ski room, ski boots dried there with the boiler, unless they were extremely wet (yay we had a couple of powder days). Parking right across the street was mostly easy, be aware that the Flegere car park is so small that during lift-running hours it overflows to the surrounding streets.
Cham All Year team is excellent, great communication and sent their very good maintenance man one evening to fix a heating glitch. Just a couple of penny pinching items let them down, perhaps specific to this apartment owner: the heating was off when we arrived and the apartment very cold, no real instructions on how to ignite it - CAY should drop by the day before to turn on and warm things up. The wifi was woeful 4Mbs day and night. CAY claimed that this was due to congestion in a busy Chamonix week, but if that were so then middle of the night 2-4am it would improve, but it didn't. The owner simply needs to pay for a decent plan. We drained all our mobile data plans.
I would rent the apartment again. I would definitely rent with CAY again, they were excellent.