I have been to Sansotei a handful of times and this review will be an overall summary of my experiences.
The broth is flavourful and the noodles are chewy (the way I like them). I have tried the black tonkotsu, tomato, and spicy tanan. Any of these choices will leave you satisfied, however the black tonkotsu has a bit of a gritty and bitter taste which may not be for everybody. My favourite is the tan tan, but it's a bit of a gamble because the supply is limited, and it may not always be available. The sides and dessert are good, but nothing to go out of your way for. The ramen is what you want.
Service was always prompt, and I love that the entire staff greets and says goodbye to you. They were especially accommodating when my friend thought she lost her ring in the back of the couch. After closing time they took it apart and checked for us. It actually did fall back there and was safely returned :)