Be prepared!
I stayed at the Hotel Whitcomb for a week for work. This wasn't out of choice - my work booked me in there and it was conveniently close to the office. Like you're doing now, I always check Trip Advisor for impartial reviews on hotels so I wanted to do some research before I came out. 
So, here is my personal take on the hotel:
Location:
Whilst convenient for work, I was a lone female traveller visiting the city for the first time. Everyone talks about this hotel being convenient for Union Square etc...but my advice? Go to a hotel near Union Square. This area is rated as the 'grittiest' area of San Francisco - be prepared to see lots of homeless people scattered outside the hotel. I am a city girl, born and raised in London but even the concierge told me not to walk around the area on my own at night and only some areas were 'ok' in the day time! Not the most confidence-inspiring thing to be told on arrival. So, even though the Bart is literally outside the hotel I didn't want to take my chances so I took a taxi everywhere. There is nothing noteworthy to see in the immediate surroundings of the hotel although there is a theatre nearby if you are planning on watching a play.
Hotel
A historic hotel this may be but it needs some serious updating. Yes, the lobby is grand and inviting. Yes, the staff are pleasant enough but the rooms are dated and need a good lick of paint, an updated heat/ventilation system and bathrooms need to be ripped out. One word of advice here: book a king room. At least you get the space and a big bed (which, by the way are comfortable). The bathroom ventilation system is so loud you may be tempted not to switch the light on and the bath was so stained and uninviting you would rather just have a shower. Note: even though the shower temperature indicated 'hot' when you turned the dial to the left, I discovered the only way to get hot water was to turn the dial to 'cold' and wait at least 5 minutes to get hot water. There is no safe in the room which I would have assumed would be a standard requirement? Don't expect room service as they do not offer this. Another word of advice: bring your own shower gel as they only provide soap. I was on the 2nd floor and my room faced the back of the hotel - I was relieved as I had read reviews that the front of the hotel facing Market Street was too noisy. Relieved until at 1am in the morning I heard a truck loading and unloading towels til 2.30am in the morning. This happened 3 nights out of my 6 night stay! Also be prepared for a stale, old smell in the hallways and the bedrooms. 
If you don't mind staying in a basic hotel and you are prepared to be in a less than attractive area than this hotel will fulfil your needs. The concierge are very friendly and always hailed a taxi for me - I also felt safe once inside the hotel.