Perfect location but at a price and not the service you would expect
I stayed in SF during 4 days and managed to find a room at the Marriot. 
Done in advance, it still did cost a mint to stay but after reviewing where I was, I kinda agreed it would have to be at a price. 
Great location, in the center of it all, in the middle of the action. You can’t go wrong position wise.
The staff is courteous, nice and helpful. But after a day at work and the buzz of the city, you expect to go back to the hotel and find a silent and distinguished place to chillax. Well, come another day..
The lobby is big but soooo impersonal, it feels like a train station. Noise, people popping from everywhere, stuff and luggage. You feel you are back at the airport.
The loud tourists from around the world (who feel because they speak another language can speak louder and nobody will hear them) or the constant agitation makes you almost want to run to your room for shelter. Well, the rooms are equally noisy and the traffic in the corridor is constant. (the hotel is longitudinal, so either you are at the end of the corridor and walk 10mn to get to your room but find peace, or you are in the middle and get all the traffic of those coming and going to their rooms)
Because you have flight crews staying there (British Airways, Air France etc...) there are always big contingents arriving early in the morning or very late at night.
The room was tidy but not exceptional, good sleeping quality but really short bed (for some reason I was expecting a real Californian king bed and ended up with the width, not the length!)
The parking situation is also a bit bizarre, as the valet is so overpriced that it is out of question, but the covered public garage (around the corner) is not the best recommended place at night. I would hate to imagine the security issues that have happened there. So, if you go the Marriot, take a cab. It will be in any case cheaper and more secure than taking your own car.
There is actually a car rental desk in the hotel, so if you are desperate for your own wheels, book it when you really need them.
So, if you are after a spa scene, a place for quiet and relaxation after a great day in a big and vibrant city, pick another place.
If you want to keep the vibe and the buzz all day and night, here you go!
I would come back (definitely for SF) but wouldn't mind trying some hotel nearby, just to check if there isn't anything better.