Good Location, Comfortable Stay
We booked the Castle Inn based on other reviews on TripAdvisor, as it seemed to be one of the only places we could find that was well priced and in a good location. We we're disappointed at all. It was out first time visiting San Francisco, so we weren't really sure what to expect. Check in was efficient, with the man on reception giving us a map of the area with information we might need (such as areas with free parking, dodgy neighbourhoods to avoid after dark etc). The rooms were large and clean, mostly your basic motel room, with a fridge, microwave and coffee machine.
The location was great, being in a more affluent neighbourhood and a fairly central place. It was a 15 minute walk to Fisherman's Wharf, close to transport lines and grocers and restaurants were easily accessed. 
Reception had a small breakfast on offer, though we mostly just grabbed a yogurt or granola bar on the way out the door each morning.
We had initially booked a 2 night stay at the Castle Inn, but due to inclement weather and our future plans, we extended our stay to a third night. The lady on reception gave us a slight discount on the room for the 3rd night.
Overall, the Castle Inn was great value, easy to locate and made for a pleasant stay in SF.