The Treehouse is absolutely amazing and we would have loved to stay at least a week. Unfortunately we were there only for two nights.
The flat is super clean and beautifully furnished. The area (Mission district) is great and thank you very much Sara for telling us, otherwise we would have missed all those gorgeous little shops and super yummy coffee places. The ice-cream place you told us about was incredible - thank you :).
Getting into downtown is very easy, we took the bus which is just a few minutes walk away. Checking out late, at 4pm, was no problem for Sara and we were really grateful as our flight was leaving in the evening.
Only thing to be aware of - the bed on the uppermost floor is up a tiny steep ladder. For us no problem but some people might not feel comfortable climbing up - it's the most beautiful sleeping space though, we loved it :).
Highly recommended and we hope to be back sometime soon.