Location: the location is very good with easy access to the MTR from Wan Chai station. Trams and buses are just a few minutes walk away.
There are many bars and clubs around the area (especially on Lockhart Road) so maybe not ideal for families.
Flat: the flat is compact but we found it OK for 3 adults with not too much luggage. The beds are small but comfortable (if you are taller than 175 cm you will probably find your feet falling off the end of the bed). The bathroom is cramped with not much space to move but we got used to it. The water pressure in the shower was good and the water temperature was stable.
The flat has a nice music hub but we couldn't make it work with our iphones - probably it works with older ipods though.
Checkin/Checkout: No issues. We didn't actually see Shanshan at all but she communicated with us very proactively and we had no issues getting into the building (I had to write my name and ID card number into a log book when we first arrived). Shanshan always responded very quickly to any messages I sent.
I would be happy to stay here again on future trips to HK.